diff --git a/devtools/client/inspector/animation/test/summary-graph_end-delay-sign_head.js b/devtools/client/inspector/animation/test/summary-graph_end-delay-sign_head.js
index f87a55442003..945cced3a486 100644
--- a/devtools/client/inspector/animation/test/summary-graph_end-delay-sign_head.js
+++ b/devtools/client/inspector/animation/test/summary-graph_end-delay-sign_head.js
@@ -66,17 +66,16 @@ async function testSummaryGraphEndDelaySign() {
         "The endDelay sign element should be in animation item element"
       );
 
-      function assertExpected(key) {
-        const actual = parseFloat(endDelaySignEl.style[key]);
-        const expected = parseFloat(expectedResult[key]);
-        ok(
-          Math.abs(actual - expected) < 0.01,
-          `${key} should be ${expected} (got ${actual})`
-        );
-      }
-
-      assertExpected(`marginInlineStart`);
-      assertExpected(`width`);
+      is(
+        endDelaySignEl.style.marginInlineStart,
+        expectedResult.marginInlineStart,
+        `marginInlineStart position should be ${expectedResult.marginInlineStart}`
+      );
+      is(
+        endDelaySignEl.style.width,
+        expectedResult.width,
+        `Width should be ${expectedResult.width}`
+      );
 
       if (expectedResult.additionalClass) {
         ok(
diff --git a/dom/animation/Animation.cpp b/dom/animation/Animation.cpp
index bc9e23aca1d6..9363cec76030 100644
--- a/dom/animation/Animation.cpp
+++ b/dom/animation/Animation.cpp
@@ -926,9 +926,9 @@ void Animation::SetCurrentTimeAsDouble(const Nullable<double>& aCurrentTime,
 
 void Animation::Tick(AnimationTimeline::TickState& aTickState) {
   if (Pending()) {
-    // Finish pending if we can, but make sure we've seen one existing tick, or
-    // we've requested to get started via SetPendingReadyTime.
-    if (!mPendingReadyTime.IsNull() || mSawTickWhilePending) {
+    // Finish pending if we can, but make sure we've seen one existing tick
+    // at least.
+    if (mSawTickWhilePending) {
       TryTriggerNow();
     }
     mSawTickWhilePending = true;
@@ -960,16 +960,6 @@ bool Animation::TryTriggerNow() {
   if (!Pending()) {
     return true;
   }
-  if (!mPendingReadyTime.IsNull()) {
-    auto timelineTime = mTimeline->ToTimelineTime(mPendingReadyTime);
-    MOZ_ASSERT(!timelineTime.IsNull(),
-               "How? This came from the timeline itself");
-    mPendingReadyTime = {};
-    if (!timelineTime.IsNull()) {
-      FinishPendingAt(timelineTime.Value());
-      return true;
-    }
-  }
   // If we don't have an active timeline we can't trigger the animation.
   if (NS_WARN_IF(!mTimeline)) {
     return false;
@@ -1459,7 +1449,7 @@ void Animation::PlayNoUpdate(ErrorResult& aRv, LimitBehavior aLimitBehavior) {
   }
 
   mPendingState = PendingState::PlayPending;
-  mPendingReadyTime = {};
+
   mSawTickWhilePending = false;
   if (Document* doc = GetRenderedDocument()) {
     if (HasFiniteTimeline()) {
@@ -1521,7 +1511,6 @@ void Animation::Pause(ErrorResult& aRv) {
   }
 
   mPendingState = PendingState::PausePending;
-  mPendingReadyTime = {};
   mSawTickWhilePending = false;
 
   // See the relevant PlayPending code for comments.
diff --git a/dom/animation/Animation.h b/dom/animation/Animation.h
index cb0859a4b68d..737be457079b 100644
--- a/dom/animation/Animation.h
+++ b/dom/animation/Animation.h
@@ -114,9 +114,6 @@ class Animation : public DOMEventTargetHelper,
   Nullable<TimeDuration> GetStartTime() const { return mStartTime; }
   Nullable<double> GetStartTimeAsDouble() const;
   void SetStartTime(const Nullable<TimeDuration>& aNewStartTime);
-  void SetPendingReadyTime(const TimeStamp& aReadyTime) {
-    mPendingReadyTime = aReadyTime;
-  }
   virtual void SetStartTimeAsDouble(const Nullable<double>& aStartTime);
 
   // This is deliberately _not_ called GetCurrentTime since that would clash
@@ -577,9 +574,6 @@ class Animation : public DOMEventTargetHelper,
   // Whether the Animation is System, ResistFingerprinting, or neither
   RTPCallerType mRTPCallerType;
 
-  // The time at which our animation should be ready.
-  TimeStamp mPendingReadyTime;
-
  private:
   // The id for this animation on the compositor.
   uint64_t mIdOnCompositor = 0;
diff --git a/dom/animation/test/chrome/test_animation_observers_async.html b/dom/animation/test/chrome/test_animation_observers_async.html
index 7b1259c713a0..0a69c12c3ef5 100644
--- a/dom/animation/test/chrome/test_animation_observers_async.html
+++ b/dom/animation/test/chrome/test_animation_observers_async.html
@@ -178,7 +178,7 @@ function runTest() {
            "getAnimations().length after transition end");
 
         // Wait for the change MutationRecord for seeking the Animation to be
-        // delivered, followed by the removal MutationRecord.
+        // delivered, followed by the the removal MutationRecord.
         return waitForFrame();
       }).then(() => {
         assert_records([{ added: [], changed: animations, removed: [] },
@@ -553,7 +553,7 @@ promise_test(t => {
       p => ({ added: [], changed: [p], removed: [] })
     );
 
-    return Promise.all(animations.map(animation => animation.finished));
+    return await_event(div, "animationend");
   }).then(() => {
     // After the changed notifications, which will be dispatched in the order that
     // the animations were seeked, we should get removal MutationRecords in order
diff --git a/gfx/layers/AnimationInfo.cpp b/gfx/layers/AnimationInfo.cpp
index 81d11f672c23..1600d40c8985 100644
--- a/gfx/layers/AnimationInfo.cpp
+++ b/gfx/layers/AnimationInfo.cpp
@@ -493,14 +493,10 @@ void AnimationInfo::AddAnimationForProperty(
     animSegment->sampleFn() = segment.mTimingFunction;
   }
 
-  if (aAnimation->Pending()) {
-    const TimeStamp readyTime =
-        aFrame->PresContext()->RefreshDriver()->MostRecentRefresh(
-            /* aEnsureTimerStarted= */ false);
-    MOZ_ASSERT(!readyTime.IsNull());
-    aAnimation->SetPendingReadyTime(readyTime);
-    MaybeStartPendingAnimation(*animation, readyTime);
-  }
+  const TimeStamp readyTime =
+      aFrame->PresContext()->RefreshDriver()->MostRecentRefresh(
+          /* aEnsureTimerStarted= */ false);
+  MaybeStartPendingAnimation(*animation, readyTime);
 }
 
 // Let's use an example to explain this function:
@@ -604,8 +600,8 @@ bool AnimationInfo::AddAnimationsForProperty(
     // Currently this only happens when the timeline is driven by a refresh
     // driver under test control. In this case, the next time the refresh
     // driver is advanced it will trigger any pending animations.
-    if (anim->Pending() && anim->GetTimeline() &&
-        !anim->GetTimeline()->TracksWallclockTime()) {
+    if (anim->Pending() &&
+        (anim->GetTimeline() && !anim->GetTimeline()->TracksWallclockTime())) {
       continue;
     }