Prevent early resolution of finished promise

Previously, a finished promise could be resolved if created while the
finish notification task was pending. This fails in the cases where the
play state is only momentarily in the finished state. For example:

anim.currentTime = ANIMATION_DURATION;
anim.finished.then(doSomething);
anim.reverse();
anim.finished.then(doSomethingElse);

In this case, doSomething should not be called.


Bug: 1005861
Change-Id: I4a04c7fc75c2ae9ee719a0444a0d22ba49fb6ead
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1928049
Commit-Queue: Kevin Ellis <kevers@chromium.org>
Reviewed-by: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718208}

third_party/blink/renderer/core/animation/animation.cc

@@ -1385,7 +1385,11 @@ ScriptPromise Animation::finished(ScriptState* script_state) {
     finished_promise_ = MakeGarbageCollected<AnimationPromise>(
         ExecutionContext::From(script_state), this,
         AnimationPromise::kFinished);
-    if (PlayStateInternal() == kFinished)
+    // Defer resolving the finished promise if the finish notification task is
+    // pending. The finished state could change before the next microtask
+    // checkpoint.
+    if (CalculateAnimationPlayState() == kFinished &&
+        !pending_finish_notification_)
       finished_promise_->Resolve(this);
   }
   return finished_promise_->Promise(script_state->World());

third_party/blink/web_tests/external/wpt/web-animations/interfaces/Animation/finished-expected.txt

-This is a testharness.js-based test.
-PASS Test pausing then playing does not change the finished promise
-PASS Test restarting a finished animation
-PASS Test restarting a reversed finished animation
-PASS Test redundant finishing of animation
-PASS Finished promise does not resolve when paused
-PASS Finished promise does not resolve when pause-pending
-PASS The finished promise is fulfilled with its Animation
-PASS finished promise is rejected when an animation is canceled by calling cancel()
-PASS canceling an already-finished animation replaces the finished promise
-PASS Test finished promise changes for animation duration changes
-PASS Test finished promise changes when playbackRate == 0
-PASS Test finished promise resolves when reaching to the natural boundary.
-PASS Test finished promise changes when a prior finished promise resolved and the animation falls out finished state
-PASS Test no new finished promise generated when finished state is checked asynchronously
-PASS Test new finished promise generated when finished state is checked synchronously
-PASS Test synchronous finished promise resolved even if finished state is changed soon
-PASS Test synchronous finished promise resolved even if asynchronous finished promise happens just before synchronous promise
-PASS Test finished promise is not resolved when the animation falls out finished state immediately
-FAIL Test finished promise is not resolved once the animation falls out finished state even though the current finished promise is generated soon after animation state became finished assert_unreached: Animation.finished should not be resolved Reached unreachable code
-PASS Finished promise should be resolved after the ready promise is resolved
-PASS Finished promise should be rejected after the ready promise is rejected
-Harness: the test ran to completion.
-