[merge to m60] cros: Do not cache |root_window| in ScreenRotationAnimator.

[merge to m60] cros: Do not cache |root_window| in ScreenRotationAnimator.

Merget to m60 on behalf of wutao

When removing a display the |root_window| might change. The cache does
not work in this situation.

TBR=oshima@chromium.org
BUG=728029
TEST=manual and ScreenRotationAnimatorSmoothAnimationTest.*

Review-Url: https://codereview.chromium.org/2910413002
Cr-Original-Commit-Position: refs/heads/master@{#476723}
Review-Url: https://codereview.chromium.org/2919393002 .
Cr-Commit-Position: refs/branch-heads/3112@{#161}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed: https://chromium.googlesource.com/chromium/src/+/6b279cbf120d6f980b40633aa6cb76d8e6af1125

[Qiang(Joe) Xu, 2017-06-05 18:36:09]

Description was changed from

==========
[merge to m60] cros: Do not cache |root_window| in ScreenRotationAnimator.

Merget to m60 on behalf of wutao

When removing a display the |root_window| might change. The cache does
not work in this situation.

TBR=oshima@chromium.org
BUG=728029
TEST=manual and ScreenRotationAnimatorSmoothAnimationTest.*

Review-Url: https://codereview.chromium.org/2910413002
Cr-Commit-Position: refs/heads/master@{#476723}
(cherry picked from commit c18f66cce628e31fbde34fa521e526fafeab4839)
==========

to

==========
[merge to m60] cros: Do not cache |root_window| in ScreenRotationAnimator.

Merget to m60 on behalf of wutao

When removing a display the |root_window| might change. The cache does
not work in this situation.

TBR=oshima@chromium.org
BUG=728029
TEST=manual and ScreenRotationAnimatorSmoothAnimationTest.*

Review-Url: https://codereview.chromium.org/2910413002
Cr-Original-Commit-Position: refs/heads/master@{#476723}
Review-Url: https://codereview.chromium.org/2919393002 .
Cr-Commit-Position: refs/branch-heads/3112@{#161}
Cr-Branched-From:
b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed:
https://chromium.googlesource.com/chromium/src/+/6b279cbf120d6f980b40633aa6cb...
==========

[Qiang(Joe) Xu, 2017-06-05 18:36:10]

Committed patchset #1 (id:1) manually as
6b279cbf120d6f980b40633aa6cb76d8e6af1125 (presubmit successful).