[BlinkGenPropertyTrees] Remove PaintPropertyChangeType::kChangedOnlyCompositedAnimationStatus

We no longer need it because we can handle change of ComputedStyle::
IsRunningXXXAnimationOnCompositor() after crrev.com/c/1509649.

Bug: 937929
Change-Id: I4dfc637d22ce5a407a8d0968452725a995f41dad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1510058
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639063}
4 files changed