Updated AnimationPlaybackEvent to return CSSNumberish for members

AnimationPlaybackEvent changed to use AnimationTimeDelta internally
and CSSNumberish externally.

Added support for scroll timelines.

Bug: 1251372
Change-Id: I2ff526dfc5d74a4b5917da2c64af29852aa9ecca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3222012
Reviewed-by: Kevin Ellis <[email protected]>
Reviewed-by: Robert Flack <[email protected]>
Commit-Queue: Jordan Taylor <[email protected]>
Cr-Commit-Position: refs/heads/main@{#933567}

scroll-animations/scroll-timelines/finish-animation.html

@@ -260,9 +260,9 @@
     'The current time is the end of the active duration in finished state.');
   assert_percents_equal(animation.startTime, -75,
     'The start time is calculated to match the current time.');
-  assert_times_equal(finishEvent.currentTime / 1000, 100,
+  assert_percents_equal(finishEvent.currentTime, 100,
     'event.currentTime is the animation current time.');
-  assert_times_equal(finishEvent.timelineTime / 1000, 25,
+  assert_percents_equal(finishEvent.timelineTime, 25,
     'event.timelineTime is timeline.currentTime');
 }, 'Finishing idle animation produces correct state and fires finish event.');
 
@@ -300,9 +300,9 @@
     'The current time is the end of active duration in finished state.');
   assert_percents_equal(animation.startTime, -75,
     'The start time is calculated to match animation current time.');
-  assert_times_equal(finishEvent.currentTime / 1000, 100,
+  assert_percents_equal(finishEvent.currentTime, 100,
     'event.currentTime is the animation current time.');
-  assert_times_equal(finishEvent.timelineTime / 1000, 25,
+  assert_percents_equal(finishEvent.timelineTime, 25,
     'event.timelineTime is timeline.currentTime');
 }, 'Finishing running animation produces correct state and fires finish event.');
 

web-animations/timing-model/timelines/update-and-send-events-replacement.html

@@ -725,8 +725,8 @@
 
   const event = await eventWatcher.wait_for('remove');
 
-  assert_equals(event.timelineTime, document.timeline.currentTime);
-  assert_equals(event.currentTime, 1);
+  assert_times_equal(event.timelineTime, document.timeline.currentTime);
+  assert_times_equal(event.currentTime, 1);
 }, 'Dispatches an event when removing');
 
 promise_test(async t => {