cc: Add UMA stats for texture copy latency.

cc: Add UMA stats for texture copy latency.

Records the time between the issue of a texture copy operation and
detecting that it has completed as measured by the GPU process.

This data is useful to determine potential driver problems related
to fences. Consistent high latency (200ms and above) for copy
operations is a strong indication of a misbehaving fence extension.

The data can also be used to determine the amount of staging
resources to use for optimal performance.

BUG=431845
Committed: https://crrev.com/63294bc251336f3e59240642676a5e758a8c2192
Cr-Commit-Position: refs/heads/master@{#304562}

[reveman, 2014-11-17 14:57:47]

reveman@chromium.org changed reviewers:
+ sievers@chromium.org

[no sievers, 2014-11-17 20:03:23]

lgtm

[reveman, 2014-11-17 20:46:44]

reveman@chromium.org changed reviewers:
+ asvitkine@chromium.org, piman@chromium.org

[reveman, 2014-11-17 20:46:44]

+piman for cc/
+asvitkine for tools/metrics/histograms/

[piman, 2014-11-17 20:50:17]

lgtm

[Alexei Svitkine (slow), 2014-11-17 22:38:43]

lgtm

[reveman, 2014-11-18 00:48:02]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-11-18 00:49:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/733053005/1

[commit-bot: I haz the power, 2014-11-18 01:33:24]

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

[commit-bot: I haz the power, 2014-11-18 01:33:25]

Try jobs failed on following builders:
  linux_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/linux_gpu_trigger...)
  win_chromium_rel on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel/...)

[reveman, 2014-11-18 02:06:14]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-11-18 02:08:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/733053005/20001

[commit-bot: I haz the power, 2014-11-18 02:57:36]

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

[commit-bot: I haz the power, 2014-11-18 02:57:40]

Try jobs failed on following builders:
  linux_chromium_asan_rel on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_rel_ng on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[reveman, 2014-11-18 03:06:58]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-11-18 03:07:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/733053005/40001

[commit-bot: I haz the power, 2014-11-18 05:06:34]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2014-11-18 05:07:23]

Patchset 3 (id:??) landed as
https://crrev.com/63294bc251336f3e59240642676a5e758a8c2192
Cr-Commit-Position: refs/heads/master@{#304562}