Bug 1999761 [wpt PR 56000] - Make scroll-timeline snapshotting tests align with spec and proposal, a=testonly

Automatic update from web-platform-tests
Make scroll-timeline snapshotting tests align with spec and proposal

According to the current spec, scroll-timelines are update after scroll
events are dispatched, but before style and layout is updated for the
frame update. With the proposed change[1] in the HTML specification,
the scroll-timelines are updated after a first style/layout update in
the resizeObserver loop.

We modify the scroll-timeline-snapshotting tests to allow them to pass
for both timings. This reveals an issue with the current Blink
implementation not matching the current spec, as we snapshot the
timelines before the scroll events are dispatched.

WebKit implements the current spec and still pass the tests after
modification.

[1] whatwg/html#11613

Bug: 384523570
Change-Id: I03b29b1f85527f9e54d597586d0764fc53f7776b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7141779
Reviewed-by: Kevin Ellis <keverschromium.org>
Commit-Queue: Rune Lillesveen <futharkchromium.org>
Cr-Commit-Position: refs/heads/main{#1543753}

--

wpt-commits: d702e50d6999b5ac1fdd815992887be83e49cbd7
wpt-pr: 56000

UltraBlame original commit: 494b53dbee4ab2d672692bb3f82b4421c2083a9c

Author: marco-c

testing/web-platform/tests/scroll-animations/scroll-timelines/scroll-timeline-snapshotting.html

@@ -36,20 +36,49 @@
 :
 /
 /
-wicg
+drafts
 .
-github
+csswg
 .
-io
+org
 /
 scroll
 -
 animations
+-
+1
 /
 #
-avoiding
+event
 -
-cycles
+loop
+"
+>
+<
+link
+rel
+=
+"
+help
+"
+href
+=
+"
+https
+:
+/
+/
+github
+.
+com
+/
+whatwg
+/
+html
+/
+pull
+/
+11613
 "
 >
 <
@@ -177,6 +206,31 @@
 script
 >
 <
+script
+src
+=
+"
+/
+css
+/
+css
+-
+scroll
+-
+snap
+/
+support
+/
+common
+.
+js
+"
+>
+<
+/
+script
+>
+<
 style
 >
 body
@@ -300,36 +354,56 @@
 to
 change
 .
-const
-startScroll
-=
-scroller
-.
-scrollTop
-;
-do
-{
 await
-waitForNextFrame
+waitForScrollEvent
 (
+document
 )
 ;
-}
-while
-(
-scroller
+/
+/
+The
+next
+frame
+the
+scroll
+changes
+the
+scroll
+-
+timelines
+should
+not
+be
+/
+/
+updated
+before
+the
+scroll
+events
+are
+dispatched
 .
-scrollTop
-=
-=
-startScroll
-)
-;
-assert_percents_equal
-(
+Store
+the
+scroll
+position
+/
+/
+from
+the
+previous
+frame
+to
+compare
+the
 timeline
+to
 .
-currentTime
+let
+scroll_percentage
+=
 (
 scroller
 .
@@ -339,6 +413,19 @@
 )
 *
 100
+;
+await
+waitForScrollEvent
+(
+document
+)
+;
+assert_percents_equal
+(
+timeline
+.
+currentTime
+scroll_percentage
 '
 Scroll
 timeline