--- a/dom/animation/test/css-animations/file_animation-finish.html
+++ b/dom/animation/test/css-animations/file_animation-finish.html
@@ -40,21 +40,20 @@ async_test(function(t) {
   div.style.animation = ANIM_PROP_VAL + ' paused';
   var animation = div.getAnimations()[0];
 
   animation.ready.then(t.step_func(function() {
     animation.finish();
     assert_equals(animation.playState, 'finished',
                   'The play state of a paused animation should become ' +
                   '"finished" after finish() is called');
-    assert_approx_equals(animation.startTime,
-                         animation.timeline.currentTime - ANIM_DURATION,
-                         0.0001,
-                         'The start time of a paused animation should be set ' +
-                         'after calling finish()');
+    assert_times_equal(animation.startTime,
+                       animation.timeline.currentTime - ANIM_DURATION,
+                       'The start time of a paused animation should be set ' +
+                       'after calling finish()');
     t.done();
   }));
 }, 'Test finish() while paused');
 
 test(function(t) {
   var div = addDiv(t);
   div.style.animation = ANIM_PROP_VAL + ' paused';
   var animation = div.getAnimations()[0];
@@ -64,21 +63,20 @@ test(function(t) {
   animation.playbackRate = 2;
 
   // While animation is still pause-pending call finish()
   animation.finish();
 
   assert_equals(animation.playState, 'finished',
                 'The play state of a pause-pending animation should become ' +
                 '"finished" after finish() is called');
-  assert_approx_equals(animation.startTime,
-                       animation.timeline.currentTime - ANIM_DURATION / 2,
-                       0.0001,
-                       'The start time of a pause-pending animation should ' +
-                       'be set after calling finish()');
+  assert_times_equal(animation.startTime,
+                     animation.timeline.currentTime - ANIM_DURATION / 2,
+                     'The start time of a pause-pending animation should ' +
+                     'be set after calling finish()');
 }, 'Test finish() while pause-pending with positive playbackRate');
 
 test(function(t) {
   var div = addDiv(t);
   div.style.animation = ANIM_PROP_VAL + ' paused';
   var animation = div.getAnimations()[0];
 
   animation.playbackRate = -2;

--- a/dom/animation/test/css-transitions/file_animation-starttime.html
+++ b/dom/animation/test/css-transitions/file_animation-starttime.html
@@ -149,17 +149,17 @@ test(function(t)
 {
   var div = addDiv(t, {'class': 'animated-div'});
   flushComputedStyle(div);
   div.style.marginLeft = '200px'; // initiate transition
 
   var animation = div.getAnimations()[0];
   var currentTime = animation.timeline.currentTime;
   animation.startTime = currentTime;
-  assert_approx_equals(animation.startTime, currentTime, 0.0001, // rounding error
+  assert_times_equal(animation.startTime, currentTime,
     'Check setting of startTime actually works');
 }, 'Sanity test to check round-tripping assigning to new animation\'s ' +
    'startTime');
 
 
 async_test(function(t) {
   var div = addDiv(t, {'class': 'animated-div'});
   var eventWatcher = new EventWatcher(t, div, 'transitionend');

--- a/testing/web-platform/tests/web-animations/interfaces/Animation/playbackRate.html
+++ b/testing/web-platform/tests/web-animations/interfaces/Animation/playbackRate.html
@@ -9,26 +9,24 @@
 <div id="log"></div>
 <script>
 'use strict';
 
 function assert_playbackrate(animation,
                              previousAnimationCurrentTime,
                              previousTimelineCurrentTime,
                              description) {
-  const accuracy = 0.001; /* accuracy of DOMHighResTimeStamp */
   const animationCurrentTimeDifference =
     animation.currentTime - previousAnimationCurrentTime;
   const timelineCurrentTimeDifference =
     animation.timeline.currentTime - previousTimelineCurrentTime;
 
-  assert_approx_equals(animationCurrentTimeDifference,
-                       timelineCurrentTimeDifference * animation.playbackRate,
-                       accuracy,
-                       description);
+  assert_times_equal(animationCurrentTimeDifference,
+                     timelineCurrentTimeDifference * animation.playbackRate,
+                     description);
 }
 
 promise_test(t => {
   const div = createDiv(t);
   const animation = div.animate(null, 100 * MS_PER_SEC);
   return animation.ready.then(() => {
     animation.currentTime = 7 * MS_PER_SEC; // ms
     animation.playbackRate = 0.5;