The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0fff6e38a8f0e7f25aff444119d5d8a8fe4f7425

commit 0fff6e38a8f0e7f25aff444119d5d8a8fe4f7425
Author: wutao <wutao@chromium.org>
Date: Fri Oct 13 01:02:20 2017

Add TrilinearFilteringObserver in scoped_layer_animation_settings.

This cl adds an TrilinearFilteringObserver to
ScopedLayerAnimationSettings so that we can AddTrilinearFilteringRequest
and RemoveTrilinearFilteringRequest at the beginning and end of the
animation.

Bug:  774242 
Test: Add new LayerAnimatorTest.
Change-Id: Ib90377529f0c782bfa755497ba3bc2891fa333db
Reviewed-on: https://chromium-review.googlesource.com/717181
Commit-Queue: Tao Wu <wutao@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508576}
[modify] https://crrev.com/0fff6e38a8f0e7f25aff444119d5d8a8fe4f7425/ui/compositor/layer_animator_unittest.cc
[modify] https://crrev.com/0fff6e38a8f0e7f25aff444119d5d8a8fe4f7425/ui/compositor/scoped_layer_animation_settings.cc
[modify] https://crrev.com/0fff6e38a8f0e7f25aff444119d5d8a8fe4f7425/ui/compositor/scoped_layer_animation_settings.h