ui: Replace std::vector with a simple array in ClipTransformRecorder.

ui: Replace std::vector with a simple array in ClipTransformRecorder.

std::vector shows up as hot in profiling as push_back() is presumably
using heap allocation. Since we don't need to support an arbitrary
number of operations on a single ClipTransformRecorder we can do better
with a simple array.

This provides a change for a single tab spinner in the UI compositor
from 0.172935 ms to 0.168272 ms which is a 3% improvement in record time
(time spent in LayerTreeHost::UpdateLayers).

R=sky
BUG=466426
Committed: https://crrev.com/71b6c7df348b822b5ed223cb8374d0cfe67f445c
Cr-Commit-Position: refs/heads/master@{#329185}

[sky, 2015-05-09 15:02:35]

LGTM

https://codereview.chromium.org/1133923002/diff/1/ui/compositor/clip_transfor...
File ui/compositor/clip_transform_recorder.cc (right):

https://codereview.chromium.org/1133923002/diff/1/ui/compositor/clip_transfor...
ui/compositor/clip_transform_recorder.cc:51: DCHECK_LT(num_closers_,
arraysize(closers_));
nit: maybe inline this in the header, eg:

void add_closer() {
  DCHECK..
  closers_[num_closers_++] = xxx;
}

[danakj, 2015-05-10 03:13:16]

https://codereview.chromium.org/1133923002/diff/1/ui/compositor/clip_transfor...
File ui/compositor/clip_transform_recorder.cc (right):

https://codereview.chromium.org/1133923002/diff/1/ui/compositor/clip_transfor...
ui/compositor/clip_transform_recorder.cc:51: DCHECK_LT(num_closers_,
arraysize(closers_));
On 2015/05/09 15:02:34, sky wrote:
> nit: maybe inline this in the header, eg:
> 
> void add_closer() {
>   DCHECK..
>   closers_[num_closers_++] = xxx;
> }

I did that at first but I kinda dislike dchecks in headers if I can avoid it to
avoid base/logging include there.

[danakj, 2015-05-10 03:13:24]

The CQ bit was checked by danakj@chromium.org

[commit-bot: I haz the power, 2015-05-10 03:15:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1133923002/1

[commit-bot: I haz the power, 2015-05-10 07:19:15]

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

[commit-bot: I haz the power, 2015-05-10 07:19:16]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_TIMED_OUT, no build URL)

[danakj, 2015-05-11 16:27:37]

The CQ bit was checked by danakj@chromium.org

[commit-bot: I haz the power, 2015-05-11 16:29:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1133923002/1

[commit-bot: I haz the power, 2015-05-11 18:11:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-11 18:12:06]

Patchset 1 (id:??) landed as
https://crrev.com/71b6c7df348b822b5ed223cb8374d0cfe67f445c
Cr-Commit-Position: refs/heads/master@{#329185}