The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/265bdd924659ecc28f1dac34653f38ce1d2fd082

commit 265bdd924659ecc28f1dac34653f38ce1d2fd082
Author: wutao <wutao@chromium.org>
Date: Fri Aug 18 17:10:40 2017

CrOS: Cache render surface in cross fade animation.

Cache render surface in animation can improve the UI performance
significantly. We have built up fundamental blocks already. In this
cl, we are caching the render surface in cross fade animation.

Performance improvement:
Linux build: ~50%
LINK: ~20%
KEVIN: ~15%

Bug:  756695 ,  753224 
Test: Tested improvement with/out cache.
Change-Id: Iad42f124b4e77c3c171bd0d59ea7b6f2831ae7f3
Reviewed-on: https://chromium-review.googlesource.com/619931
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495591}
[modify] https://crrev.com/265bdd924659ecc28f1dac34653f38ce1d2fd082/ash/wm/window_animations.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9fac7d30ac7eb7ad8950758aa0672a3a3881ee00

commit 9fac7d30ac7eb7ad8950758aa0672a3a3881ee00
Author: wutao <wutao@chromium.org>
Date: Mon Oct 09 19:25:41 2017

CrOS: Only caching render surface when there is an opacity animation.

When there is an opacity for a hierarchy of layers, it requires that a
render surface (RS) is created to produce correct output. In this case,
caching RS is always a benefit as we need a RS anyhow and it just avoids
having to recreate it from the hierarchy of layers each frame of the
animation.

the layer with opacity animation.

Bug:  756695 
Test: Tested in cross fade animation, only cached render surface of
Change-Id: Ia01e04954b69207530556569cf6f5770a0dc021b
Reviewed-on: https://chromium-review.googlesource.com/703917
Reviewed-by: David Reveman <reveman@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#507444}
[modify] https://crrev.com/9fac7d30ac7eb7ad8950758aa0672a3a3881ee00/ash/wm/window_animations.cc