Reland "Reenable scroll-animations/element-based-offset tests"

The patch fixes the underlying problem in the element-based-offset
tests, whereby a scroll timeline can be created before layout resulting
in a zero scroll range.  This patch adds a forced layout.

Revert CL: https://chromium-review.googlesource.com/c/chromium/src/+/2483585

Bug: 1080609
Change-Id: I44c6186f535e713d49a9ce6cab4d6aa68c302889
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2484267Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Kevin Ellis <kevers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818480}

third_party/blink/web_tests/TestExpectations

@@ -145,7 +145,7 @@ virtual/composite-after-paint/paint/frames/* [ Pass ]
 virtual/composite-after-paint/scrollingcoordinator/* [ Pass ]
 # --- End CompositeAfterPaint Tests --
 
-# --- BEGIN OOP-R Canvas tests --- 
+# --- BEGIN OOP-R Canvas tests ---
 crbug.com/1081534 [ Win7 ] virtual/oopr-canvas2d/fast/canvas/canvas-composite-video-shadow.html [ Pass Failure ]
 crbug.com/1081534 [ Win ] virtual/oopr-canvas2d/fast/canvas/canvas-clearRect-first.html [ Failure ]
 crbug.com/1081534 [ Win ] virtual/oopr-canvas2d/fast/canvas/canvas-clearRect-with-clip.html [ Failure ]
@@ -6118,9 +6118,6 @@ crbug.com/1011811 http/tests/devtools/network/network-xhr-data-received-async-re
 crbug.com/1011811 http/tests/devtools/network/download.js [ Pass Failure ]
 crbug.com/1011811 http/tests/devtools/sxg/sxg-disable-cache.js [ Pass Failure ]
 
-crbug.com/1080609 virtual/threaded/external/wpt/scroll-animations/element-based-offset.html [ Pass Failure ]
-crbug.com/1080609 virtual/threaded/external/wpt/scroll-animations/element-based-offset-clamp.html [ Pass Failure ]
-
 # Fails when test moved to use full compositor pipe.
 crbug.com/1085832 [ Fuchsia ] images/size-failure.html [ Timeout ]
 

third_party/blink/web_tests/external/wpt/scroll-animations/element-based-offset-clamp.html

@@ -7,25 +7,19 @@
 <script src="testcommon.js"></script>
 
 <style>
+/*
+ * Overflow hidden prevents user scroll including mouse wheel; however, the
+ * element is still a scrollable container and can be scrolled programmatically.
+ * Removing the visible scrollbars in this manner simplifies the position
+ * calculations in the text.
+ */
 .scroller {
-  overflow: scroll;
+  overflow: hidden;
   height: 500px;
   width: 500px;
   will-change: transform;
 }
 
-/* Disable scrollbars to simplify the calculations in the test. */
-.scroller {
-  scrollbar-width: 0;
-}
-/*
-Chrome does not support scrollbar-width so we use this non-standard property
-until it does.
-*/
-.scroller::-webkit-scrollbar {
-  display: none;
-}
-
 .contents {
   height: 1200px;
   width: 1200px;
@@ -82,6 +76,10 @@ until it does.
 
       const target = scroller.querySelector("#target");
 
+      // Force layout before creating the scroll timeline to ensure the correct
+      // scroll range.
+      target.offsetHeight;
+
       const timeline = createScrollTimeline(t, {
         scrollSource: scroller,
         orientation: config.orientation,
@@ -212,4 +210,4 @@ until it does.
       createScrollAnimationTest(description, config);
     }
   }
-</script>
\ No newline at end of file
+</script>

third_party/blink/web_tests/external/wpt/scroll-animations/element-based-offset.html

@@ -66,7 +66,11 @@
       t.add_cleanup(() => scroller.remove());
 
       const start = scroller.querySelector("#start");
-      const end = scroller.querySelector("#end")
+      const end = scroller.querySelector("#end");
+
+      // Force layout to ensure the scroll timeline gets the correct scroll
+      // range.
+      start.offsetHeight;
 
       const timeline = createScrollTimeline(t, {
         scrollSource: scroller,
@@ -202,4 +206,4 @@
       createScrollAnimationTest(description, config);
     }
   }
-</script>
\ No newline at end of file
+</script>