--- a/testing/web-platform/tests/web-animations/resources/keyframe-tests.js
+++ b/testing/web-platform/tests/web-animations/resources/keyframe-tests.js
@@ -1,533 +1,533 @@
-"use strict";
+'use strict';
 
 // ==============================
 //
 // Common keyframe test data
 //
 // ==============================
 
 
 // ------------------------------
 //  Composite values
 // ------------------------------
 
 const gGoodKeyframeCompositeValueTests = [
-  "replace", "add", "accumulate", undefined
+  'replace', 'add', 'accumulate', undefined
 ];
 
 const gGoodOptionsCompositeValueTests = [
-  "replace", "add", "accumulate"
+  'replace', 'add', 'accumulate'
 ];
 
 const gBadCompositeValueTests = [
-  "unrecognised", "replace ", "Replace", null
+  'unrecognised', 'replace ', 'Replace', null
 ];
 
 // ------------------------------
 //  Keyframes
 // ------------------------------
 
 const gEmptyKeyframeListTests = [
   [],
   null,
   undefined,
 ];
 
 const gPropertyIndexedKeyframesTests = [
-  { desc:   "a one property two value property-indexed keyframes specification",
-    input:  { left: ["10px", "20px"] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear",
-               left: "10px" },
-             { offset: null, computedOffset: 1, easing: "linear",
-               left: "20px" }] },
-  { desc:   "a one shorthand property two value property-indexed keyframes"
-            + " specification",
-    input:  { margin: ["10px", "10px 20px 30px 40px"] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear",
-               margin: "10px" },
-             { offset: null, computedOffset: 1, easing: "linear",
-               margin: "10px 20px 30px 40px" }] },
-  { desc:   "a two property (one shorthand and one of its longhand components)"
-            + " two value property-indexed keyframes specification",
-    input:  { marginTop: ["50px", "60px"],
-              margin: ["10px", "10px 20px 30px 40px"] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear",
-               marginTop: "50px", margin: "10px" },
-             { offset: null, computedOffset: 1, easing: "linear",
-               marginTop: "60px", margin: "10px 20px 30px 40px" }] },
-  { desc:   "a two property two value property-indexed keyframes specification",
-    input:  { left: ["10px", "20px"],
-              top: ["30px", "40px"] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear",
-               left: "10px", top: "30px" },
-             { offset: null, computedOffset: 1, easing: "linear",
-               left: "20px", top: "40px" }] },
-  { desc:   "a two property property-indexed keyframes specification with"
-            + " different numbers of values",
-    input:  { left: ["10px", "20px", "30px"],
-              top: ["40px", "50px"] },
-    output: [{ offset: null, computedOffset: 0.0, easing: "linear",
-               left: "10px", top: "40px" },
-             { offset: null, computedOffset: 0.5, easing: "linear",
-               left: "20px" },
-             { offset: null, computedOffset: 1.0, easing: "linear",
-               left: "30px", top: "50px" }] },
-  { desc:   "a property-indexed keyframes specification with an invalid value",
-    input:  { left: ["10px", "20px", "30px", "40px", "50px"],
-              top:  ["15px", "25px", "invalid", "45px", "55px"] },
-    output: [{ offset: null, computedOffset: 0.00, easing: "linear",
-               left: "10px", top: "15px" },
-             { offset: null, computedOffset: 0.25, easing: "linear",
-               left: "20px", top: "25px" },
-             { offset: null, computedOffset: 0.50, easing: "linear",
-               left: "30px" },
-             { offset: null, computedOffset: 0.75, easing: "linear",
-               left: "40px", top: "45px" },
-             { offset: null, computedOffset: 1.00, easing: "linear",
-               left: "50px", top: "55px" }] },
-  { desc:   "a one property two value property-indexed keyframes specification"
-            + " that needs to stringify its values",
+  { desc:   'a one property two value property-indexed keyframes specification',
+    input:  { left: ['10px', '20px'] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear',
+               left: '10px' },
+             { offset: null, computedOffset: 1, easing: 'linear',
+               left: '20px' }] },
+  { desc:   'a one shorthand property two value property-indexed keyframes'
+            + ' specification',
+    input:  { margin: ['10px', '10px 20px 30px 40px'] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear',
+               margin: '10px' },
+             { offset: null, computedOffset: 1, easing: 'linear',
+               margin: '10px 20px 30px 40px' }] },
+  { desc:   'a two property (one shorthand and one of its longhand components)'
+            + ' two value property-indexed keyframes specification',
+    input:  { marginTop: ['50px', '60px'],
+              margin: ['10px', '10px 20px 30px 40px'] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear',
+               marginTop: '50px', margin: '10px' },
+             { offset: null, computedOffset: 1, easing: 'linear',
+               marginTop: '60px', margin: '10px 20px 30px 40px' }] },
+  { desc:   'a two property two value property-indexed keyframes specification',
+    input:  { left: ['10px', '20px'],
+              top: ['30px', '40px'] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear',
+               left: '10px', top: '30px' },
+             { offset: null, computedOffset: 1, easing: 'linear',
+               left: '20px', top: '40px' }] },
+  { desc:   'a two property property-indexed keyframes specification with'
+            + ' different numbers of values',
+    input:  { left: ['10px', '20px', '30px'],
+              top: ['40px', '50px'] },
+    output: [{ offset: null, computedOffset: 0.0, easing: 'linear',
+               left: '10px', top: '40px' },
+             { offset: null, computedOffset: 0.5, easing: 'linear',
+               left: '20px' },
+             { offset: null, computedOffset: 1.0, easing: 'linear',
+               left: '30px', top: '50px' }] },
+  { desc:   'a property-indexed keyframes specification with an invalid value',
+    input:  { left: ['10px', '20px', '30px', '40px', '50px'],
+              top:  ['15px', '25px', 'invalid', '45px', '55px'] },
+    output: [{ offset: null, computedOffset: 0.00, easing: 'linear',
+               left: '10px', top: '15px' },
+             { offset: null, computedOffset: 0.25, easing: 'linear',
+               left: '20px', top: '25px' },
+             { offset: null, computedOffset: 0.50, easing: 'linear',
+               left: '30px' },
+             { offset: null, computedOffset: 0.75, easing: 'linear',
+               left: '40px', top: '45px' },
+             { offset: null, computedOffset: 1.00, easing: 'linear',
+               left: '50px', top: '55px' }] },
+  { desc:   'a one property two value property-indexed keyframes specification'
+            + ' that needs to stringify its values',
     input:  { opacity: [0, 1] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear",
-               opacity: "0" },
-             { offset: null, computedOffset: 1, easing: "linear",
-               opacity: "1" }] },
-  { desc:   "a property-indexed keyframes specification with a CSS variable"
-            + " reference",
-    input:  { left: [ "var(--dist)", "calc(var(--dist) + 100px)" ] },
-    output: [{ offset: null, computedOffset: 0.0, easing: "linear",
-               left: "var(--dist)" },
-             { offset: null, computedOffset: 1.0, easing: "linear",
-               left: "calc(var(--dist) + 100px)" }] },
-  { desc:   "a property-indexed keyframes specification with a CSS variable"
-            + " reference in a shorthand property",
-    input:  { margin: [ "var(--dist)", "calc(var(--dist) + 100px)" ] },
-    output: [{ offset: null, computedOffset: 0.0, easing: "linear",
-               margin: "var(--dist)" },
-             { offset: null, computedOffset: 1.0, easing: "linear",
-               margin: "calc(var(--dist) + 100px)" }] },
-  { desc:   "a one property one value property-indexed keyframes specification",
-    input:  { left: ["10px"] },
-    output: [{ offset: null, computedOffset: 1, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a one property one non-array value property-indexed keyframes"
-            + " specification",
-    input:  { left: "10px" },
-    output: [{ offset: null, computedOffset: 1, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a one property two value property-indexed keyframes specification"
-            + " where the first value is invalid",
-    input:  { left: ["invalid", "10px"] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear" },
-             { offset: null, computedOffset: 1, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a one property two value property-indexed keyframes specification"
-            + " where the second value is invalid",
-    input:  { left: ["10px", "invalid"] },
-    output: [{ offset: null, computedOffset: 0, easing: "linear",
-               left: "10px" },
-             { offset: null, computedOffset: 1, easing: "linear" }] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear',
+               opacity: '0' },
+             { offset: null, computedOffset: 1, easing: 'linear',
+               opacity: '1' }] },
+  { desc:   'a property-indexed keyframes specification with a CSS variable'
+            + ' reference',
+    input:  { left: [ 'var(--dist)', 'calc(var(--dist) + 100px)' ] },
+    output: [{ offset: null, computedOffset: 0.0, easing: 'linear',
+               left: 'var(--dist)' },
+             { offset: null, computedOffset: 1.0, easing: 'linear',
+               left: 'calc(var(--dist) + 100px)' }] },
+  { desc:   'a property-indexed keyframes specification with a CSS variable'
+            + ' reference in a shorthand property',
+    input:  { margin: [ 'var(--dist)', 'calc(var(--dist) + 100px)' ] },
+    output: [{ offset: null, computedOffset: 0.0, easing: 'linear',
+               margin: 'var(--dist)' },
+             { offset: null, computedOffset: 1.0, easing: 'linear',
+               margin: 'calc(var(--dist) + 100px)' }] },
+  { desc:   'a one property one value property-indexed keyframes specification',
+    input:  { left: ['10px'] },
+    output: [{ offset: null, computedOffset: 1, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a one property one non-array value property-indexed keyframes'
+            + ' specification',
+    input:  { left: '10px' },
+    output: [{ offset: null, computedOffset: 1, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a one property two value property-indexed keyframes specification'
+            + ' where the first value is invalid',
+    input:  { left: ['invalid', '10px'] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear' },
+             { offset: null, computedOffset: 1, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a one property two value property-indexed keyframes specification'
+            + ' where the second value is invalid',
+    input:  { left: ['10px', 'invalid'] },
+    output: [{ offset: null, computedOffset: 0, easing: 'linear',
+               left: '10px' },
+             { offset: null, computedOffset: 1, easing: 'linear' }] },
 ];
 
 const gKeyframeSequenceTests = [
-  { desc:   "a one property one keyframe sequence",
-    input:  [{ offset: 1, left: "10px" }],
-    output: [{ offset: 1, computedOffset: 1, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a one property two keyframe sequence",
-    input:  [{ offset: 0, left: "10px" },
-             { offset: 1, left: "20px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear", left: "10px" },
-             { offset: 1, computedOffset: 1, easing: "linear", left: "20px" }]
+  { desc:   'a one property one keyframe sequence',
+    input:  [{ offset: 1, left: '10px' }],
+    output: [{ offset: 1, computedOffset: 1, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a one property two keyframe sequence',
+    input:  [{ offset: 0, left: '10px' },
+             { offset: 1, left: '20px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear', left: '10px' },
+             { offset: 1, computedOffset: 1, easing: 'linear', left: '20px' }]
   },
-  { desc:   "a two property two keyframe sequence",
-    input:  [{ offset: 0, left: "10px", top: "30px" },
-             { offset: 1, left: "20px", top: "40px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               left: "10px", top: "30px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               left: "20px", top: "40px" }] },
-  { desc:   "a one shorthand property two keyframe sequence",
-    input:  [{ offset: 0, margin: "10px" },
-             { offset: 1, margin: "20px 30px 40px 50px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               margin: "10px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               margin: "20px 30px 40px 50px" }] },
-  { desc:   "a two property (a shorthand and one of its component longhands)"
-            + " two keyframe sequence",
-    input:  [{ offset: 0, margin: "10px", marginTop: "20px" },
-             { offset: 1, marginTop: "70px", margin: "30px 40px 50px 60px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               margin: "10px", marginTop: "20px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               marginTop: "70px", margin: "30px 40px 50px 60px" }] },
-  { desc:   "a keyframe sequence with duplicate values for a given interior"
-            + " offset",
-    input:  [{ offset: 0.0, left: "10px" },
-             { offset: 0.5, left: "20px" },
-             { offset: 0.5, left: "30px" },
-             { offset: 0.5, left: "40px" },
-             { offset: 1.0, left: "50px" }],
-    output: [{ offset: 0.0, computedOffset: 0.0, easing: "linear",
-               left: "10px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               left: "20px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               left: "30px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               left: "40px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "linear",
-               left: "50px" }] },
-  { desc:   "a keyframe sequence with duplicate values for offsets 0 and 1",
-    input:  [{ offset: 0, left: "10px" },
-             { offset: 0, left: "20px" },
-             { offset: 0, left: "30px" },
-             { offset: 1, left: "40px" },
-             { offset: 1, left: "50px" },
-             { offset: 1, left: "60px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear", left: "10px" },
-             { offset: 0, computedOffset: 0, easing: "linear", left: "20px" },
-             { offset: 0, computedOffset: 0, easing: "linear", left: "30px" },
-             { offset: 1, computedOffset: 1, easing: "linear", left: "40px" },
-             { offset: 1, computedOffset: 1, easing: "linear", left: "50px" },
-             { offset: 1, computedOffset: 1, easing: "linear", left: "60px" }]
+  { desc:   'a two property two keyframe sequence',
+    input:  [{ offset: 0, left: '10px', top: '30px' },
+             { offset: 1, left: '20px', top: '40px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               left: '10px', top: '30px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               left: '20px', top: '40px' }] },
+  { desc:   'a one shorthand property two keyframe sequence',
+    input:  [{ offset: 0, margin: '10px' },
+             { offset: 1, margin: '20px 30px 40px 50px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               margin: '10px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               margin: '20px 30px 40px 50px' }] },
+  { desc:   'a two property (a shorthand and one of its component longhands)'
+            + ' two keyframe sequence',
+    input:  [{ offset: 0, margin: '10px', marginTop: '20px' },
+             { offset: 1, marginTop: '70px', margin: '30px 40px 50px 60px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               margin: '10px', marginTop: '20px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               marginTop: '70px', margin: '30px 40px 50px 60px' }] },
+  { desc:   'a keyframe sequence with duplicate values for a given interior'
+            + ' offset',
+    input:  [{ offset: 0.0, left: '10px' },
+             { offset: 0.5, left: '20px' },
+             { offset: 0.5, left: '30px' },
+             { offset: 0.5, left: '40px' },
+             { offset: 1.0, left: '50px' }],
+    output: [{ offset: 0.0, computedOffset: 0.0, easing: 'linear',
+               left: '10px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               left: '20px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               left: '30px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               left: '40px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'linear',
+               left: '50px' }] },
+  { desc:   'a keyframe sequence with duplicate values for offsets 0 and 1',
+    input:  [{ offset: 0, left: '10px' },
+             { offset: 0, left: '20px' },
+             { offset: 0, left: '30px' },
+             { offset: 1, left: '40px' },
+             { offset: 1, left: '50px' },
+             { offset: 1, left: '60px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear', left: '10px' },
+             { offset: 0, computedOffset: 0, easing: 'linear', left: '20px' },
+             { offset: 0, computedOffset: 0, easing: 'linear', left: '30px' },
+             { offset: 1, computedOffset: 1, easing: 'linear', left: '40px' },
+             { offset: 1, computedOffset: 1, easing: 'linear', left: '50px' },
+             { offset: 1, computedOffset: 1, easing: 'linear', left: '60px' }]
   },
-  { desc:   "a two property four keyframe sequence",
-    input:  [{ offset: 0, left: "10px" },
-             { offset: 0, top: "20px" },
-             { offset: 1, top: "30px" },
-             { offset: 1, left: "40px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear", left: "10px" },
-             { offset: 0, computedOffset: 0, easing: "linear", top: "20px" },
-             { offset: 1, computedOffset: 1, easing: "linear", top: "30px" },
-             { offset: 1, computedOffset: 1, easing: "linear", left: "40px" }]
+  { desc:   'a two property four keyframe sequence',
+    input:  [{ offset: 0, left: '10px' },
+             { offset: 0, top: '20px' },
+             { offset: 1, top: '30px' },
+             { offset: 1, left: '40px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear', left: '10px' },
+             { offset: 0, computedOffset: 0, easing: 'linear', top: '20px' },
+             { offset: 1, computedOffset: 1, easing: 'linear', top: '30px' },
+             { offset: 1, computedOffset: 1, easing: 'linear', left: '40px' }]
   },
-  { desc:   "a single keyframe sequence with omitted offset",
-    input:  [{ left: "10px" }],
-    output: [{ offset: null, computedOffset: 1, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a single keyframe sequence with null offset",
-    input:  [{ offset: null, left: "10px" }],
-    output: [{ offset: null, computedOffset: 1, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a single keyframe sequence with string offset",
-    input:  [{ offset: '0.5', left: "10px" }],
-    output: [{ offset: 0.5, computedOffset: 0.5, easing: "linear",
-               left: "10px" }] },
-  { desc:   "a one property keyframe sequence with some omitted offsets",
-    input:  [{ offset: 0.00, left: "10px" },
-             { offset: 0.25, left: "20px" },
-             { left: "30px" },
-             { left: "40px" },
-             { offset: 1.00, left: "50px" }],
-    output: [{ offset: 0.00, computedOffset: 0.00, easing: "linear",
-               left: "10px" },
-             { offset: 0.25, computedOffset: 0.25, easing: "linear",
-               left: "20px" },
-             { offset: null, computedOffset: 0.50, easing: "linear",
-               left: "30px" },
-             { offset: null, computedOffset: 0.75, easing: "linear",
-               left: "40px" },
-             { offset: 1.00, computedOffset: 1.00, easing: "linear",
-               left: "50px" }] },
-  { desc:   "a one property keyframe sequence with some null offsets",
-    input:  [{ offset: 0.00, left: "10px" },
-             { offset: 0.25, left: "20px" },
-             { offset: null, left: "30px" },
-             { offset: null, left: "40px" },
-             { offset: 1.00, left: "50px" }],
-    output: [{ offset: 0.00, computedOffset: 0.00, easing: "linear",
-               left: "10px" },
-             { offset: 0.25, computedOffset: 0.25, easing: "linear",
-               left: "20px" },
-             { offset: null, computedOffset: 0.50, easing: "linear",
-               left: "30px" },
-             { offset: null, computedOffset: 0.75, easing: "linear",
-               left: "40px" },
-             { offset: 1.00, computedOffset: 1.00, easing: "linear",
-               left: "50px" }] },
-  { desc:   "a two property keyframe sequence with some omitted offsets",
-    input:  [{ offset: 0.00, left: "10px", top: "20px" },
-             { offset: 0.25, left: "30px" },
-             { left: "40px" },
-             { left: "50px", top: "60px" },
-             { offset: 1.00, left: "70px", top: "80px" }],
-    output: [{ offset: 0.00, computedOffset: 0.00, easing: "linear",
-               left: "10px", top: "20px" },
-             { offset: 0.25, computedOffset: 0.25, easing: "linear",
-               left: "30px" },
-             { offset: null, computedOffset: 0.50, easing: "linear",
-               left: "40px" },
-             { offset: null, computedOffset: 0.75, easing: "linear",
-               left: "50px", top: "60px" },
-             { offset: 1.00, computedOffset: 1.00, easing: "linear",
-               left: "70px", top: "80px" }] },
-  { desc:   "a one property keyframe sequence with all omitted offsets",
-    input:  [{ left: "10px" },
-             { left: "20px" },
-             { left: "30px" },
-             { left: "40px" },
-             { left: "50px" }],
-    output: [{ offset: null, computedOffset: 0.00, easing: "linear",
-               left: "10px" },
-             { offset: null, computedOffset: 0.25, easing: "linear",
-               left: "20px" },
-             { offset: null, computedOffset: 0.50, easing: "linear",
-               left: "30px" },
-             { offset: null, computedOffset: 0.75, easing: "linear",
-               left: "40px" },
-             { offset: null, computedOffset: 1.00, easing: "linear",
-               left: "50px" }] },
-  { desc:   "a keyframe sequence with different easing values, but the same"
-            + " easing value for a given offset",
-    input:  [{ offset: 0.0, easing: "ease",     left: "10px"},
-             { offset: 0.0, easing: "ease",     top: "20px"},
-             { offset: 0.5, easing: "linear",   left: "30px" },
-             { offset: 0.5, easing: "linear",   top: "40px" },
-             { offset: 1.0, easing: "step-end", left: "50px" },
-             { offset: 1.0, easing: "step-end", top: "60px" }],
-    output: [{ offset: 0.0, computedOffset: 0.0, easing: "ease",
-               left: "10px" },
-             { offset: 0.0, computedOffset: 0.0, easing: "ease",
-               top: "20px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               left: "30px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               top: "40px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "steps(1)",
-               left: "50px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "steps(1)",
-               top: "60px" }] },
-  { desc:   "a keyframe sequence with different composite values, but the"
-            + " same composite value for a given offset",
-    input:  [{ offset: 0.0, composite: "replace", left: "10px" },
-             { offset: 0.0, composite: "replace", top: "20px" },
-             { offset: 0.5, composite: "add",     left: "30px" },
-             { offset: 0.5, composite: "add",     top: "40px" },
-             { offset: 1.0, composite: "replace", left: "50px" },
-             { offset: 1.0, composite: "replace", top: "60px" }],
-    output: [{ offset: 0.0, computedOffset: 0.0, easing: "linear",
-               composite: "replace", left: "10px" },
-             { offset: 0.0, computedOffset: 0.0, easing: "linear",
-               composite: "replace", top: "20px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               composite: "add", left: "30px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               composite: "add", top: "40px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "linear",
-               composite: "replace", left: "50px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "linear",
-               composite: "replace", top: "60px" }] },
-  { desc:   "a one property two keyframe sequence that needs to stringify"
-            + " its values",
+  { desc:   'a single keyframe sequence with omitted offset',
+    input:  [{ left: '10px' }],
+    output: [{ offset: null, computedOffset: 1, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a single keyframe sequence with null offset',
+    input:  [{ offset: null, left: '10px' }],
+    output: [{ offset: null, computedOffset: 1, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a single keyframe sequence with string offset',
+    input:  [{ offset: '0.5', left: '10px' }],
+    output: [{ offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               left: '10px' }] },
+  { desc:   'a one property keyframe sequence with some omitted offsets',
+    input:  [{ offset: 0.00, left: '10px' },
+             { offset: 0.25, left: '20px' },
+             { left: '30px' },
+             { left: '40px' },
+             { offset: 1.00, left: '50px' }],
+    output: [{ offset: 0.00, computedOffset: 0.00, easing: 'linear',
+               left: '10px' },
+             { offset: 0.25, computedOffset: 0.25, easing: 'linear',
+               left: '20px' },
+             { offset: null, computedOffset: 0.50, easing: 'linear',
+               left: '30px' },
+             { offset: null, computedOffset: 0.75, easing: 'linear',
+               left: '40px' },
+             { offset: 1.00, computedOffset: 1.00, easing: 'linear',
+               left: '50px' }] },
+  { desc:   'a one property keyframe sequence with some null offsets',
+    input:  [{ offset: 0.00, left: '10px' },
+             { offset: 0.25, left: '20px' },
+             { offset: null, left: '30px' },
+             { offset: null, left: '40px' },
+             { offset: 1.00, left: '50px' }],
+    output: [{ offset: 0.00, computedOffset: 0.00, easing: 'linear',
+               left: '10px' },
+             { offset: 0.25, computedOffset: 0.25, easing: 'linear',
+               left: '20px' },
+             { offset: null, computedOffset: 0.50, easing: 'linear',
+               left: '30px' },
+             { offset: null, computedOffset: 0.75, easing: 'linear',
+               left: '40px' },
+             { offset: 1.00, computedOffset: 1.00, easing: 'linear',
+               left: '50px' }] },
+  { desc:   'a two property keyframe sequence with some omitted offsets',
+    input:  [{ offset: 0.00, left: '10px', top: '20px' },
+             { offset: 0.25, left: '30px' },
+             { left: '40px' },
+             { left: '50px', top: '60px' },
+             { offset: 1.00, left: '70px', top: '80px' }],
+    output: [{ offset: 0.00, computedOffset: 0.00, easing: 'linear',
+               left: '10px', top: '20px' },
+             { offset: 0.25, computedOffset: 0.25, easing: 'linear',
+               left: '30px' },
+             { offset: null, computedOffset: 0.50, easing: 'linear',
+               left: '40px' },
+             { offset: null, computedOffset: 0.75, easing: 'linear',
+               left: '50px', top: '60px' },
+             { offset: 1.00, computedOffset: 1.00, easing: 'linear',
+               left: '70px', top: '80px' }] },
+  { desc:   'a one property keyframe sequence with all omitted offsets',
+    input:  [{ left: '10px' },
+             { left: '20px' },
+             { left: '30px' },
+             { left: '40px' },
+             { left: '50px' }],
+    output: [{ offset: null, computedOffset: 0.00, easing: 'linear',
+               left: '10px' },
+             { offset: null, computedOffset: 0.25, easing: 'linear',
+               left: '20px' },
+             { offset: null, computedOffset: 0.50, easing: 'linear',
+               left: '30px' },
+             { offset: null, computedOffset: 0.75, easing: 'linear',
+               left: '40px' },
+             { offset: null, computedOffset: 1.00, easing: 'linear',
+               left: '50px' }] },
+  { desc:   'a keyframe sequence with different easing values, but the same'
+            + ' easing value for a given offset',
+    input:  [{ offset: 0.0, easing: 'ease',     left: '10px'},
+             { offset: 0.0, easing: 'ease',     top: '20px'},
+             { offset: 0.5, easing: 'linear',   left: '30px' },
+             { offset: 0.5, easing: 'linear',   top: '40px' },
+             { offset: 1.0, easing: 'step-end', left: '50px' },
+             { offset: 1.0, easing: 'step-end', top: '60px' }],
+    output: [{ offset: 0.0, computedOffset: 0.0, easing: 'ease',
+               left: '10px' },
+             { offset: 0.0, computedOffset: 0.0, easing: 'ease',
+               top: '20px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               left: '30px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               top: '40px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'steps(1)',
+               left: '50px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'steps(1)',
+               top: '60px' }] },
+  { desc:   'a keyframe sequence with different composite values, but the'
+            + ' same composite value for a given offset',
+    input:  [{ offset: 0.0, composite: 'replace', left: '10px' },
+             { offset: 0.0, composite: 'replace', top: '20px' },
+             { offset: 0.5, composite: 'add',     left: '30px' },
+             { offset: 0.5, composite: 'add',     top: '40px' },
+             { offset: 1.0, composite: 'replace', left: '50px' },
+             { offset: 1.0, composite: 'replace', top: '60px' }],
+    output: [{ offset: 0.0, computedOffset: 0.0, easing: 'linear',
+               composite: 'replace', left: '10px' },
+             { offset: 0.0, computedOffset: 0.0, easing: 'linear',
+               composite: 'replace', top: '20px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               composite: 'add', left: '30px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               composite: 'add', top: '40px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'linear',
+               composite: 'replace', left: '50px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'linear',
+               composite: 'replace', top: '60px' }] },
+  { desc:   'a one property two keyframe sequence that needs to stringify'
+            + ' its values',
     input:  [{ offset: 0, opacity: 0 },
              { offset: 1, opacity: 1 }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear", opacity: "0" },
-             { offset: 1, computedOffset: 1, easing: "linear", opacity: "1" }]
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear', opacity: '0' },
+             { offset: 1, computedOffset: 1, easing: 'linear', opacity: '1' }]
   },
-  { desc:   "a keyframe sequence with a CSS variable reference",
-    input:  [{ left: "var(--dist)" },
-             { left: "calc(var(--dist) + 100px)" }],
-    output: [{ offset: null, computedOffset: 0.0, easing: "linear",
-               left: "var(--dist)" },
-             { offset: null, computedOffset: 1.0, easing: "linear",
-               left: "calc(var(--dist) + 100px)" }] },
-  { desc:   "a keyframe sequence with a CSS variable reference in a shorthand"
-            + " property",
-    input:  [{ margin: "var(--dist)" },
-             { margin: "calc(var(--dist) + 100px)" }],
-    output: [{ offset: null, computedOffset: 0.0, easing: "linear",
-               margin: "var(--dist)" },
-             { offset: null, computedOffset: 1.0, easing: "linear",
-               margin: "calc(var(--dist) + 100px)" }] },
-  { desc:   "a keyframe sequence where shorthand precedes longhand",
-    input:  [{ offset: 0, margin: "10px", marginRight: "20px" },
-             { offset: 1, margin: "30px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               margin: "10px", marginRight: "20px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               margin: "30px" }] },
-  { desc:   "a keyframe sequence where longhand precedes shorthand",
-    input:  [{ offset: 0, marginRight: "20px", margin: "10px" },
-             { offset: 1, margin: "30px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               marginRight: "20px", margin: "10px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               margin: "30px" }] },
-  { desc:   "a keyframe sequence where lesser shorthand precedes greater"
-            + " shorthand",
+  { desc:   'a keyframe sequence with a CSS variable reference',
+    input:  [{ left: 'var(--dist)' },
+             { left: 'calc(var(--dist) + 100px)' }],
+    output: [{ offset: null, computedOffset: 0.0, easing: 'linear',
+               left: 'var(--dist)' },
+             { offset: null, computedOffset: 1.0, easing: 'linear',
+               left: 'calc(var(--dist) + 100px)' }] },
+  { desc:   'a keyframe sequence with a CSS variable reference in a shorthand'
+            + ' property',
+    input:  [{ margin: 'var(--dist)' },
+             { margin: 'calc(var(--dist) + 100px)' }],
+    output: [{ offset: null, computedOffset: 0.0, easing: 'linear',
+               margin: 'var(--dist)' },
+             { offset: null, computedOffset: 1.0, easing: 'linear',
+               margin: 'calc(var(--dist) + 100px)' }] },
+  { desc:   'a keyframe sequence where shorthand precedes longhand',
+    input:  [{ offset: 0, margin: '10px', marginRight: '20px' },
+             { offset: 1, margin: '30px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               margin: '10px', marginRight: '20px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               margin: '30px' }] },
+  { desc:   'a keyframe sequence where longhand precedes shorthand',
+    input:  [{ offset: 0, marginRight: '20px', margin: '10px' },
+             { offset: 1, margin: '30px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               marginRight: '20px', margin: '10px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               margin: '30px' }] },
+  { desc:   'a keyframe sequence where lesser shorthand precedes greater'
+            + ' shorthand',
     input:  [{ offset: 0,
-               borderLeft: "1px solid rgb(1, 2, 3)",
-               border: "2px dotted rgb(4, 5, 6)" },
-             { offset: 1, border: "3px dashed rgb(7, 8, 9)" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               borderLeft: "1px solid rgb(1, 2, 3)",
-               border: "2px dotted rgb(4, 5, 6)" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               border: "3px dashed rgb(7, 8, 9)" }] },
-  { desc:   "a keyframe sequence where greater shorthand precedes lesser"
-            + " shorthand",
-    input:  [{ offset: 0, border: "2px dotted rgb(4, 5, 6)",
-               borderLeft: "1px solid rgb(1, 2, 3)" },
-             { offset: 1, border: "3px dashed rgb(7, 8, 9)" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               border: "2px dotted rgb(4, 5, 6)",
-               borderLeft: "1px solid rgb(1, 2, 3)" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               border: "3px dashed rgb(7, 8, 9)" }] },
-  { desc:   "a two property keyframe sequence where one property is missing"
-            + " from the first keyframe",
-    input:  [{ offset: 0, left: "10px" },
-             { offset: 1, left: "20px", top: "30px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear", left: "10px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               left: "20px", top: "30px" }] },
-  { desc:   "a two property keyframe sequence where one property is missing"
-            + " from the last keyframe",
-    input:  [{ offset: 0, left: "10px", top: "20px" },
-             { offset: 1, left: "30px" }],
-    output: [{ offset: 0, computedOffset: 0, easing: "linear",
-               left: "10px" , top: "20px" },
-             { offset: 1, computedOffset: 1, easing: "linear",
-               left: "30px" }] },
-  { desc:   "a keyframe sequence with repeated values at offset 1 with"
-            + " different easings",
-    input:  [{ offset: 0.0, left: "100px", easing: "ease" },
-             { offset: 0.0, left: "200px", easing: "ease" },
-             { offset: 0.5, left: "300px", easing: "linear" },
-             { offset: 1.0, left: "400px", easing: "ease-out" },
-             { offset: 1.0, left: "500px", easing: "step-end" }],
-    output: [{ offset: 0.0, computedOffset: 0.0, easing: "ease",
-               left: "100px" },
-             { offset: 0.0, computedOffset: 0.0, easing: "ease",
-               left: "200px" },
-             { offset: 0.5, computedOffset: 0.5, easing: "linear",
-               left: "300px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "ease-out",
-               left: "400px" },
-             { offset: 1.0, computedOffset: 1.0, easing: "steps(1)",
-               left: "500px" }] },
+               borderLeft: '1px solid rgb(1, 2, 3)',
+               border: '2px dotted rgb(4, 5, 6)' },
+             { offset: 1, border: '3px dashed rgb(7, 8, 9)' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               borderLeft: '1px solid rgb(1, 2, 3)',
+               border: '2px dotted rgb(4, 5, 6)' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               border: '3px dashed rgb(7, 8, 9)' }] },
+  { desc:   'a keyframe sequence where greater shorthand precedes lesser'
+            + ' shorthand',
+    input:  [{ offset: 0, border: '2px dotted rgb(4, 5, 6)',
+               borderLeft: '1px solid rgb(1, 2, 3)' },
+             { offset: 1, border: '3px dashed rgb(7, 8, 9)' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               border: '2px dotted rgb(4, 5, 6)',
+               borderLeft: '1px solid rgb(1, 2, 3)' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               border: '3px dashed rgb(7, 8, 9)' }] },
+  { desc:   'a two property keyframe sequence where one property is missing'
+            + ' from the first keyframe',
+    input:  [{ offset: 0, left: '10px' },
+             { offset: 1, left: '20px', top: '30px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear', left: '10px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               left: '20px', top: '30px' }] },
+  { desc:   'a two property keyframe sequence where one property is missing'
+            + ' from the last keyframe',
+    input:  [{ offset: 0, left: '10px', top: '20px' },
+             { offset: 1, left: '30px' }],
+    output: [{ offset: 0, computedOffset: 0, easing: 'linear',
+               left: '10px' , top: '20px' },
+             { offset: 1, computedOffset: 1, easing: 'linear',
+               left: '30px' }] },
+  { desc:   'a keyframe sequence with repeated values at offset 1 with'
+            + ' different easings',
+    input:  [{ offset: 0.0, left: '100px', easing: 'ease' },
+             { offset: 0.0, left: '200px', easing: 'ease' },
+             { offset: 0.5, left: '300px', easing: 'linear' },
+             { offset: 1.0, left: '400px', easing: 'ease-out' },
+             { offset: 1.0, left: '500px', easing: 'step-end' }],
+    output: [{ offset: 0.0, computedOffset: 0.0, easing: 'ease',
+               left: '100px' },
+             { offset: 0.0, computedOffset: 0.0, easing: 'ease',
+               left: '200px' },
+             { offset: 0.5, computedOffset: 0.5, easing: 'linear',
+               left: '300px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'ease-out',
+               left: '400px' },
+             { offset: 1.0, computedOffset: 1.0, easing: 'steps(1)',
+               left: '500px' }] },
 ];
 
 const gInvalidKeyframesTests = [
-  { desc:     "keyframes with an out-of-bounded positive offset",
+  { desc:     'keyframes with an out-of-bounded positive offset',
     input:    [ { opacity: 0 },
                 { opacity: 0.5, offset: 2 },
                 { opacity: 1 } ],
-    expected: { name: "TypeError" } },
-  { desc:     "keyframes with an out-of-bounded negative offset",
+    expected: { name: 'TypeError' } },
+  { desc:     'keyframes with an out-of-bounded negative offset',
     input:    [ { opacity: 0 },
                 { opacity: 0.5, offset: -1 },
                 { opacity: 1 } ],
-    expected: { name: "TypeError" } },
-  { desc:     "keyframes not loosely sorted by offset",
+    expected: { name: 'TypeError' } },
+  { desc:     'keyframes not loosely sorted by offset',
     input:    [ { opacity: 0, offset: 1 },
                 { opacity: 1, offset: 0 } ],
-    expected: { name: "TypeError" } },
-  { desc:     "property-indexed keyframes with an invalid easing value",
+    expected: { name: 'TypeError' } },
+  { desc:     'property-indexed keyframes with an invalid easing value',
     input:    { opacity: [ 0, 0.5, 1 ],
-                easing: "inherit" },
-    expected: { name: "TypeError" } },
-  { desc:     "a keyframe sequence with an invalid easing value",
-    input:    [ { opacity: 0, easing: "jumpy" },
+                easing: 'inherit' },
+    expected: { name: 'TypeError' } },
+  { desc:     'a keyframe sequence with an invalid easing value',
+    input:    [ { opacity: 0, easing: 'jumpy' },
                 { opacity: 1 } ],
-    expected: { name: "TypeError" } },
-  { desc:     "keyframes with an invalid composite value",
-    input:    [ { opacity: 0, composite: "alternate" },
+    expected: { name: 'TypeError' } },
+  { desc:     'keyframes with an invalid composite value',
+    input:    [ { opacity: 0, composite: 'alternate' },
                 { opacity: 1 } ],
-    expected: { name: "TypeError" } }
+    expected: { name: 'TypeError' } }
 ];
 
 // ------------------------------
 //  KeyframeEffectOptions
 // ------------------------------
 
 const gKeyframeEffectOptionTests = [
-  { desc:     "an empty KeyframeEffectOptions object",
+  { desc:     'an empty KeyframeEffectOptions object',
     input:    { },
     expected: { } },
-  { desc:     "a normal KeyframeEffectOptions object",
+  { desc:     'a normal KeyframeEffectOptions object',
     input:    { delay: 1000,
-                fill: "auto",
+                fill: 'auto',
                 iterations: 5.5,
-                duration: "auto",
-                direction: "alternate" },
+                duration: 'auto',
+                direction: 'alternate' },
     expected: { delay: 1000,
-                fill: "auto",
+                fill: 'auto',
                 iterations: 5.5,
-                duration: "auto",
-                direction: "alternate" } },
-  { desc:     "a double value",
+                duration: 'auto',
+                direction: 'alternate' } },
+  { desc:     'a double value',
     input:    3000,
     expected: { duration: 3000 } },
-  { desc:     "+Infinity",
+  { desc:     '+Infinity',
     input:    Infinity,
     expected: { duration: Infinity } },
-  { desc:     "an Infinity duration",
+  { desc:     'an Infinity duration',
     input:    { duration: Infinity },
     expected: { duration: Infinity } },
-  { desc:     "an auto duration",
-    input:    { duration: "auto" },
-    expected: { duration: "auto" } },
-  { desc:     "an Infinity iterations",
+  { desc:     'an auto duration',
+    input:    { duration: 'auto' },
+    expected: { duration: 'auto' } },
+  { desc:     'an Infinity iterations',
     input:    { iterations: Infinity },
     expected: { iterations: Infinity } },
-  { desc:     "an auto fill",
-    input:    { fill: "auto" },
-    expected: { fill: "auto" } },
-  { desc:     "a forwards fill",
-    input:    { fill: "forwards" },
-    expected: { fill: "forwards" } }
+  { desc:     'an auto fill',
+    input:    { fill: 'auto' },
+    expected: { fill: 'auto' } },
+  { desc:     'a forwards fill',
+    input:    { fill: 'forwards' },
+    expected: { fill: 'forwards' } }
 ];
 
 const gInvalidKeyframeEffectOptionTests = [
-  { desc:     "-Infinity",
+  { desc:     '-Infinity',
     input:    -Infinity,
-    expected: { name: "TypeError" } },
-  { desc:     "NaN",
+    expected: { name: 'TypeError' } },
+  { desc:     'NaN',
     input:    NaN,
-    expected: { name: "TypeError" } },
-  { desc:     "a negative value",
+    expected: { name: 'TypeError' } },
+  { desc:     'a negative value',
     input:    -1,
-    expected: { name: "TypeError" } },
-  { desc:     "a negative Infinity duration",
+    expected: { name: 'TypeError' } },
+  { desc:     'a negative Infinity duration',
     input:    { duration: -Infinity },
-    expected: { name: "TypeError" } },
-  { desc:     "a NaN duration",
+    expected: { name: 'TypeError' } },
+  { desc:     'a NaN duration',
     input:    { duration: NaN },
-    expected: { name: "TypeError" } },
-  { desc:     "a negative duration",
+    expected: { name: 'TypeError' } },
+  { desc:     'a negative duration',
     input:    { duration: -1 },
-    expected: { name: "TypeError" } },
-  { desc:     "a string duration",
-    input:    { duration: "merrychristmas" },
-    expected: { name: "TypeError" } },
-  { desc:     "a negative Infinity iterations",
+    expected: { name: 'TypeError' } },
+  { desc:     'a string duration',
+    input:    { duration: 'merrychristmas' },
+    expected: { name: 'TypeError' } },
+  { desc:     'a negative Infinity iterations',
     input:    { iterations: -Infinity},
-    expected: { name: "TypeError" } },
-  { desc:     "a NaN iterations",
+    expected: { name: 'TypeError' } },
+  { desc:     'a NaN iterations',
     input:    { iterations: NaN },
-    expected: { name: "TypeError" } },
-  { desc:     "a negative iterations",
+    expected: { name: 'TypeError' } },
+  { desc:     'a negative iterations',
     input:    { iterations: -1 },
-    expected: { name: "TypeError" } },
-  { desc:     "a blank easing",
-    input:    { easing: "" },
-    expected: { name: "TypeError" } },
-  { desc:     "an unrecognized easing",
-    input:    { easing: "unrecognised" },
-    expected: { name: "TypeError" } },
-  { desc:     "an 'initial' easing",
-    input:    { easing: "initial" },
-    expected: { name: "TypeError" } },
-  { desc:     "an 'inherit' easing",
-    input:    { easing: "inherit" },
-    expected: { name: "TypeError" } },
-  { desc:     "a variable easing",
-    input:    { easing: "var(--x)" },
-    expected: { name: "TypeError" } },
-  { desc:     "a multi-value easing",
-    input:    { easing: "ease-in-out, ease-out" },
-    expected: { name: "TypeError" } }
+    expected: { name: 'TypeError' } },
+  { desc:     'a blank easing',
+    input:    { easing: '' },
+    expected: { name: 'TypeError' } },
+  { desc:     'an unrecognized easing',
+    input:    { easing: 'unrecognised' },
+    expected: { name: 'TypeError' } },
+  { desc:     'an \'initial\' easing',
+    input:    { easing: 'initial' },
+    expected: { name: 'TypeError' } },
+  { desc:     'an \'inherit\' easing',
+    input:    { easing: 'inherit' },
+    expected: { name: 'TypeError' } },
+  { desc:     'a variable easing',
+    input:    { easing: 'var(--x)' },
+    expected: { name: 'TypeError' } },
+  { desc:     'a multi-value easing',
+    input:    { easing: 'ease-in-out, ease-out' },
+    expected: { name: 'TypeError' } }
 ];

--- a/testing/web-platform/tests/web-animations/resources/keyframe-utils.js
+++ b/testing/web-platform/tests/web-animations/resources/keyframe-utils.js
@@ -1,9 +1,9 @@
-"use strict";
+'use strict';
 
 // =======================================
 //
 // Utility functions for testing keyframes
 //
 // =======================================
 
 
@@ -12,17 +12,17 @@
 // ------------------------------
 
 /**
  * Test equality between two lists of computed keyframes
  * @param {Array.<ComputedKeyframe>} a - actual computed keyframes
  * @param {Array.<ComputedKeyframe>} b - expected computed keyframes
  */
 function assert_frame_lists_equal(a, b) {
-  assert_equals(a.length, b.length, "number of frames");
+  assert_equals(a.length, b.length, 'number of frames');
   for (let i = 0; i < Math.min(a.length, b.length); i++) {
     assert_frames_equal(a[i], b[i], `ComputedKeyframe #${i}`);
   }
 }
 
 /** Helper for assert_frame_lists_equal */
 function assert_frames_equal(a, b, name) {
   assert_equals(Object.keys(a).sort().toString(),