Mac overlays: Isolate partial swap support

Mac overlays: Isolate partial swap support

The logic to maintain a CALayer tree for partial swap support is
complicated and should be removed, but that would compromise battery
usage. Once the CoreAniamtion renderer is handling ~99% of the frames,
we can remove it. In the mean time, isolate it.

Create a CALayerPartialDamageTree to track the layer tree of partially
swapped backbuffers. Do this in-place to minimize diffs, so that this
patch can be reasonably reviewed. A follow-on patch will move it to
a separate file.

Slightly reorganize the logic so that CALayerPartialDamageTree matches
the general structure of CALayerTree, where this a pending (not swapped)
tree, a tree for each pending swap, and a tree for what is currently
being displayed.

BUG=533681
Committed: https://crrev.com/8aa00fc2a374fca3e9b9f34d838db7bb5f4fc088
Cr-Commit-Position: refs/heads/master@{#371831}

[ccameron, 2016-01-27 04:07:14]

ccameron@chromium.org changed reviewers:
+ erikchen@chromium.org

[ccameron, 2016-01-27 04:07:14]

Paying penance for this monstrosity. Hopefully soon we can delete it and pretend
it never happened.

[erikchen, 2016-01-27 16:41:14]

lgtm

[ccameron, 2016-01-27 18:40:55]

Thanks!

[ccameron, 2016-01-27 18:41:01]

The CQ bit was checked by ccameron@chromium.org

[commit-bot: I haz the power, 2016-01-27 18:42:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1640093002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1640093002/20001

[commit-bot: I haz the power, 2016-01-27 18:50:25]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-01-27 18:51:33]

Description was changed from

==========
Mac overlays: Isolate partial swap support

The logic to maintain a CALayer tree for partial swap support is
complicated and should be removed, but that would compromise battery
usage. Once the CoreAniamtion renderer is handling ~99% of the frames,
we can remove it. In the mean time, isolate it.

Create a CALayerPartialDamageTree to track the layer tree of partially
swapped backbuffers. Do this in-place to minimize diffs, so that this
patch can be reasonably reviewed. A follow-on patch will move it to
a separate file.

Slightly reorganize the logic so that CALayerPartialDamageTree matches
the general structure of CALayerTree, where this a pending (not swapped)
tree, a tree for each pending swap, and a tree for what is currently
being displayed.

BUG=533681
==========

to

==========
Mac overlays: Isolate partial swap support

The logic to maintain a CALayer tree for partial swap support is
complicated and should be removed, but that would compromise battery
usage. Once the CoreAniamtion renderer is handling ~99% of the frames,
we can remove it. In the mean time, isolate it.

Create a CALayerPartialDamageTree to track the layer tree of partially
swapped backbuffers. Do this in-place to minimize diffs, so that this
patch can be reasonably reviewed. A follow-on patch will move it to
a separate file.

Slightly reorganize the logic so that CALayerPartialDamageTree matches
the general structure of CALayerTree, where this a pending (not swapped)
tree, a tree for each pending swap, and a tree for what is currently
being displayed.

BUG=533681

Committed: https://crrev.com/8aa00fc2a374fca3e9b9f34d838db7bb5f4fc088
Cr-Commit-Position: refs/heads/master@{#371831}
==========

[commit-bot: I haz the power, 2016-01-27 18:51:36]

Patchset 2 (id:??) landed as
https://crrev.com/8aa00fc2a374fca3e9b9f34d838db7bb5f4fc088
Cr-Commit-Position: refs/heads/master@{#371831}