--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -145220,21 +145220,21 @@
    "b45b864be8c189b5b4113e9a7f3820fd8a08df6a",
    "testharness"
   ],
   "XMLHttpRequest/open-url-multi-window.htm": [
    "28603b8d225367ba648bb9271dec5cb3da73d733",
    "testharness"
   ],
   "XMLHttpRequest/open-url-redirected-worker-origin.htm": [
-   "d92032b7a81bcea83ee03df3affe0e25263328b0",
+   "877d6bd227709cc3ada32493ba6cc86683efade9",
    "testharness"
   ],
   "XMLHttpRequest/open-url-worker-origin.htm": [
-   "e4db65c7c0a98d7f5aa84eac01705259f377f44b",
+   "f105c0e4b249f82545f2763c4b1a23a3a217e3a7",
    "testharness"
   ],
   "XMLHttpRequest/open-url-worker-simple.htm": [
    "224c1502970253197c670bfb04efa15708e034d5",
    "testharness"
   ],
   "XMLHttpRequest/open-user-password-non-same-origin.htm": [
    "9e28bf35af12bb962fdfd2213d7e20e031a29703",
@@ -148248,17 +148248,17 @@
    "3c203529afca2f6b2a075eb8a42bf2206e4f16af",
    "support"
   ],
   "battery-status/support-window-open.html": [
    "61b61d09a21daee964e0ebd26f7bdfdd1964c8ae",
    "support"
   ],
   "beacon/headers/header-content-type.html": [
-   "51fc2b60a8e3e7c92208a8308e3f2156c363d205",
+   "5753ef82d17941aaf0c929da8952f88aa4186f02",
    "testharness"
   ],
   "beacon/headers/header-referrer-no-referrer-when-downgrade.https.html": [
    "273c7d0110d5efc9fac0029cd257256894d3eb4b",
    "testharness"
   ],
   "beacon/headers/header-referrer-no-referrer.html": [
    "26a0a9453b36efbadb05c8185efe7f9a0d9d54c9",
@@ -173800,17 +173800,17 @@
    "9a7ed5f97f7eff3f6711325dea7dcca1323d3bde",
    "support"
   ],
   "encrypted-media/scripts/playback-temporary.js": [
    "ac2f3395cd63f1fe4c243265c59fc3f503f09926",
    "support"
   ],
   "encrypted-media/scripts/requestmediakeysystemaccess.js": [
-   "6a40a2db2ae0657bda978bcaee1a12f7670634bb",
+   "1a17a323605ff3882b8e9d8ac4b48f1a2d592d97",
    "support"
   ],
   "encrypted-media/scripts/reset-src-after-setmediakeys.js": [
    "5c82378ce1dd5c9991b78668d7cfd0e02c2d1b5e",
    "support"
   ],
   "encrypted-media/scripts/setmediakeys-again-after-playback.js": [
    "fc6557f201aad3dfcd5df83a96d40fdbf752d009",
@@ -219052,21 +219052,21 @@
    "eee8ff07b3ec5e83e5f18305f5bc00eb72468443",
    "testharness"
   ],
   "web-animations/animation-model/animation-types/interpolation-per-property.html": [
    "55100f7d505bc8cbc966ced0d1337ed78534a553",
    "testharness"
   ],
   "web-animations/animation-model/animation-types/property-list.js": [
-   "83a52204cc36f6b757129dae947f03f6a8748bde",
+   "a6860f4971e06078b5abdd57b3d7f57c0adff51e",
    "support"
   ],
   "web-animations/animation-model/animation-types/property-types.js": [
-   "66c606f9451cc30ba6d23bcfffcb61871283b0b8",
+   "0c6ae747d483ba276749f9b7760c513eb0d7992c",
    "support"
   ],
   "web-animations/animation-model/animation-types/spacing-keyframes-filters.html": [
    "bd771a8a18245560221d92ea3495f81918c09848",
    "testharness"
   ],
   "web-animations/animation-model/animation-types/spacing-keyframes-shapes.html": [
    "03c3ab6815cfa96c07d5f95b6059fb276c50a25f",
@@ -233820,17 +233820,17 @@
    "a819c0e16d9054bb97595c596151172d0bd2f948",
    "testharness"
   ],
   "workers/constructors/SharedWorker/null": [
    "f6b1ea1bc04df6207506ae337eb258beb0fb5108",
    "support"
   ],
   "workers/constructors/SharedWorker/null-arguments.html": [
-   "9034961b63d92367fd2066be86179a9265fc6503",
+   "58a6bcb00711dc7fab954a8e030b9073a16d6bd7",
    "testharness"
   ],
   "workers/constructors/SharedWorker/number-arguments.html": [
    "6506f2dd0e43681255d3c35d860f3faa3a1bdd87",
    "testharness"
   ],
   "workers/constructors/SharedWorker/port-onmessage.html": [
    "36a90dd7bb4548125beeea8b6f3435ff0283f4e8",
@@ -233928,17 +233928,17 @@
    "478f18c9032dccd6b9daaab1ad8cfba51fb045d6",
    "testharness"
   ],
   "workers/constructors/Worker/undefined": [
    "5e15cbad6bc958f2146c3c94c925619bae36f6c6",
    "support"
   ],
   "workers/constructors/Worker/unexpected-self-properties.worker.js": [
-   "5ae6b1457d41b9c1cf8d9bf3a0b3abedc77cad72",
+   "73bc10eac3f8659e1f5e41d3e8a86beec05ed0bc",
    "testharness"
   ],
   "workers/constructors/Worker/unresolvable-url.html": [
    "a585e2aa6314087be5f126f4ad8a86a1c5deb7a7",
    "testharness"
   ],
   "workers/constructors/Worker/use-base-url.html": [
    "23ed9eb3cf4b65bdd0301570677a6d89af0e551b",

--- a/testing/web-platform/meta/web-animations/animation-model/animation-types/accumulation-per-property.html.ini
+++ b/testing/web-platform/meta/web-animations/animation-model/animation-types/accumulation-per-property.html.ini
@@ -1,5 +1,9 @@
 [accumulation-per-property.html]
   type: testharness
   [column-gap: "normal" onto "200px"]
     expected: FAIL
 
+  [font-stretch (type: fontStretch) has testAccumulation function]
+    expected: FAIL
+    bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1363246
+

--- a/testing/web-platform/meta/web-animations/animation-model/animation-types/addition-per-property.html.ini
+++ b/testing/web-platform/meta/web-animations/animation-model/animation-types/addition-per-property.html.ini
@@ -1,7 +1,10 @@
 prefs: [layout.css.contain.enabled:true, layout.css.initial-letter.enabled:true, layout.css.overflow-clip-box.enabled:true, layout.css.shape-outside.enabled:true]
 [addition-per-property.html]
   type: testharness
   [column-gap: "normal" onto "200px"]
     expected: FAIL
     bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1356241
 
+  [font-stretch (type: fontStretch) has testAddition function]
+    expected: FAIL
+    bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1363246

--- a/testing/web-platform/tests/web-animations/animation-model/animation-types/property-list.js
+++ b/testing/web-platform/tests/web-animations/animation-model/animation-types/property-list.js
@@ -527,18 +527,17 @@ var gCSSProperties = {
   },
   'font-size-adjust': {
     // https://drafts.csswg.org/css-fonts-3/#propdef-font-size-adjust
     types: [
     ]
   },
   'font-stretch': {
     // https://drafts.csswg.org/css-fonts-3/#propdef-font-stretch
-    types: [
-    ]
+    types: [ 'fontStretch' ]
   },
   'font-style': {
     // https://drafts.csswg.org/css-fonts/#propdef-font-style
     types: [
       { type: 'discrete', options: [ [ 'italic', 'oblique' ] ] }
     ]
   },
   'float': {

--- a/testing/web-platform/tests/web-animations/animation-model/animation-types/property-types.js
+++ b/testing/web-platform/tests/web-animations/animation-model/animation-types/property-types.js
@@ -1605,16 +1605,45 @@ const dasharrayType = {
     this.testAdditionOrAccumulation(property, setup, 'add');
   },
 
   testAccumulation: function(property, setup) {
     this.testAdditionOrAccumulation(property, setup, 'accumulate');
   },
 }
 
+const fontStretchType = {
+  testInterpolation: function(property, setup) {
+    test(function(t) {
+      var idlName = propertyToIDL(property);
+      var target = createTestElement(t, setup);
+      var animation = target.animate({ [idlName]:
+                                         ['ultra-condensed',
+					  'extra-condensed'] },
+                                     { duration: 1000, fill: 'both' });
+	testAnimationSamples(
+          animation, idlName,
+          [{ time: 499,  expected: 'ultra-condensed' },
+           { time: 500,  expected: 'extra-condensed' }]);
+    }, property + ' supports animating as a font-stretch (adjacent values)');
+
+    test(function(t) {
+      var idlName = propertyToIDL(property);
+      var target = createTestElement(t, setup);
+      var animation = target.animate({ [idlName]:
+                                         ['ultra-condensed',
+					  'condensed'] },
+                                     { duration: 1000, fill: 'both' });
+	testAnimationSamples(
+          animation, idlName,
+          [{ time: 500,  expected: 'extra-condensed' }]);
+    }, property + ' supports animating as a font-stretch (between value)');
+  },
+}
+
 const types = {
   color: colorType,
   discrete: discreteType,
   filterList: filterListType,
   integer: integerType,
   positiveInteger: positiveIntegerType,
   length: lengthType,
   percentage: percentageType,
@@ -1624,10 +1653,11 @@ const types = {
   opacity: opacityType,
   transformList: transformListType,
   visibility: visibilityType,
   boxShadowList: boxShadowListType,
   textShadowList: textShadowListType,
   rect: rectType,
   position: positionType,
   dasharray: dasharrayType,
+  fontStretch: fontStretchType,
 };