Revert "Skip static animations on compositor and main" (#44970)

This reverts commit 3690cd7872423e81e74dc66f9886e355a7c1b659.

Reason for revert: virtual/threaded-no-composited-antialiasing/animations
tests started failing on multiple builders after this CL.
* https://ci.chromium.org/ui/p/chromium/builders/ci/linux-bfcache-rel
* https://ci.chromium.org/ui/p/chromium/builders/ci/mac11-arm64-rel-tests
* https://ci.chromium.org/ui/p/chromium/builders/ci/mac12-arm64-rel-tests
* https://ci.chromium.org/ui/p/chromium/builders/ci/Linux%20Tests

Original change's description:
> Skip static animations on compositor and main
>
> An animation with empty keyframes or with keyframes whose property
> values are identical between frames previously ran as a normal
> animation. As there is no visual change other than at a phase boundary,
> these animations do not need to run on the compositor, and only need
> to be scheduled on the main thread at phase boundaries.
>
> This is the first step in optimizing no-op animations. A follow up
> patch will short-circuit sampling when the property value is constant.
> Another patch will refine the rules for background color compositing
> to only consider dynamic properties.  Finally, metrics will be added
> to track shorthand expansion of CSS properties, which is likely the
> most common source of static properties in CSS animations.
>
> Bug: 40728212
> Change-Id: I1baff2d0d26400f91f12d4cac2141e9bb101b3d0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5328026
> Reviewed-by: Ian Clelland <iclelland@chromium.org>
> Reviewed-by: Robert Flack <flackr@chromium.org>
> Commit-Queue: Kevin Ellis <kevers@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1268998}

Bug: 40728212
Change-Id: Idccfa689d7a3b6e6ee9e2b6a5d109c94a4d3870b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5349489
Owners-Override: Michael Ershov <miersh@google.com>
Commit-Queue: Michael Ershov <miersh@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Michael Ershov <miersh@google.com>
Cr-Commit-Position: refs/heads/main@{#1269503}

Co-authored-by: Michael Ershov <miersh@google.com>

css/css-transforms/animation/support/transform-interpolation-reftests.js

@@ -127,13 +127,6 @@ const midpointOptions = {
   delay: -duration/2
 };
 
-// Constant-valued animation using the ending keyframe's value.
-const referenceOptions = {
-  easing: 'steps(1, jump-start)',
-  duration: duration,
-  delay: -duration/2
-}
-
 // Similar to midpointOptions, but to produce the interpolation result
 // at -1 instead of the interpolation result at 0.5.  This easing curve
 // has zero slope at its midpoint of -100% (though does have curvature).
@@ -176,8 +169,9 @@ async function createTests(tests) {
   takeScreenshot();
 }
 
-// Create references using a constant-valued animation  to avoid rounding and
-// anti-aliasing differences between animated and non-animated pathways.
+// Create references using an animation with identical keyframes for start
+// and end so as to avoid rounding and anti-aliasing differences between
+// animated and non-animated pathways.
 async function createRefs(tests) {
   styleBody();
   for (const obj of tests) {
@@ -187,8 +181,8 @@ async function createRefs(tests) {
     initialStyle(div);
     finalStyle(div);
     var anim = div.animate(
-        {transform: ['none', test[midIndex]]},
-        referenceOptions);
+        {transform: [test[midIndex], test[midIndex]]},
+        midpointOptions);
     await anim.ready;
   }
 

dom/events/scrolling/scroll_support.js

@@ -120,7 +120,7 @@ function waitForCompositorCommit() {
 // deferred running the tests until after paint holding.
 async function waitForCompositorReady() {
   const animation =
-      document.body.animate({ opacity: [ 0, 1 ] }, {duration: 1 });
+      document.body.animate({ opacity: [ 1, 1 ] }, {duration: 1 });
   return animation.finished;
 }
 

web-animations/testcommon.js

@@ -331,7 +331,7 @@ function assert_phase(animation, phase) {
 // crbug.com/1378671
 async function waitForCompositorReady() {
   const animation =
-      document.body.animate({ opacity: [ 0, 1 ] }, {duration: 1 });
+      document.body.animate({ opacity: [ 1, 1 ] }, {duration: 1 });
   return animation.finished;
 }