Add screen rotation animator lock.

[Landed another one: https://codereview.chromium.org/2872123002/]

Add screen rotation animator lock.

When screen rotates, wallpaper needs to be resized accordingly, which
takes time. Adding a screen rotation animator lock, allows us to second
copy output request after the wallpaper is resized.

BUG=678763
TEST=tested manual on minnie.

[wutao, 2017-04-28 18:04:27]

wutao@chromium.org changed reviewers:
+ oshima@chromium.org

[wutao, 2017-04-28 18:04:28]

Hi Oshima,

I am adding this animator lock for screen rotation.
We can add multiple locks if we want to wait for multiple event to finish. In
this cl, only wait for wallpaper resize and calculate color.

Thanks,
Tao

[wutao, 2017-04-28 18:29:49]

The CQ bit was checked by wutao@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-04-28 18:30:59]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-28 19:54:38]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-04-28 19:54:39]

Dry run: Try jobs failed on following builders:
  linux_chromium_asan_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[oshima, 2017-04-28 20:18:39]

This looks more complicated than necessary.

Is there a reason why ScreenRotationAnimator owns comopstior lock instead of
WallpaperController?

[wutao, 2017-04-28 20:37:45]

On 2017/04/28 20:18:39, oshima wrote:
> This looks more complicated than necessary.
> 
> Is there a reason why ScreenRotationAnimator owns comopstior lock instead of
> WallpaperController?

comopstior lock* do you mean animator lock?

We only need this lock during screen rotation animation.
We can simple have a wallpaper lock, during rotation animation and query that
lock state (or notified by observer). But if we want to adding more waiting
events (other resize), we need to implement lock for each of the event.

In current design, it can observe multiple events, not only to the wallpaper.
That is why I call it animator lock.
For example, if we want to wait ARC, we can create a animator lock and injected
to ARC and at ARC side, lock/unlock it.

For the ownership of the animator lock, one concern is that when wallpaper
resize (requests an screen rotation animator lock), the animator may not be
available. Also we do not know which display animator it will call. (animator
will be created on the first time of rotation for each display).
It will be much easier to hold the ownership of all the animator locks by the
animator.

[oshima_google, 2017-04-28 20:44:05]

I meant compositor lock. Why not just use the same mechanism that we're using
in renderer? That'd reduce the dependency and code.

[wutao, 2017-05-26 03:07:14]

Description was changed from

==========
Add screen rotation animator lock.

When screen rotates, wallpaper needs to be resized accordingly, which
takes time. Adding a screen rotation animator lock, allows us to second
copy output request after the wallpaper is resized.

BUG=678763
TEST=tested manual on minnie.
==========

to

==========
[Landed another one: https://codereview.chromium.org/2872123002/]

Add screen rotation animator lock.

When screen rotates, wallpaper needs to be resized accordingly, which
takes time. Adding a screen rotation animator lock, allows us to second
copy output request after the wallpaper is resized.

BUG=678763
TEST=tested manual on minnie.
==========