Update UMA mapping.

Update UMA mapping.

UseCounter added for setting AudioBufferSourceNode.buffer more than
once.

BUG=448960
Committed: https://crrev.com/10ab4e95843c5a4759282d695a9680ee9085dd01
Cr-Commit-Position: refs/heads/master@{#314390}

[Raymond Toy, 2015-01-29 23:37:32]

rtoy@chromium.org changed reviewers:
+ asvitkine@chromium.org

[Raymond Toy, 2015-01-29 23:37:32]

PTAL.

[Alexei Svitkine (slow), 2015-01-30 00:46:34]

lgtm

[Raymond Toy, 2015-01-30 16:44:36]

The CQ bit was checked by rtoy@chromium.org

[commit-bot: I haz the power, 2015-01-30 16:45:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885183002/1

[commit-bot: I haz the power, 2015-01-30 18:40:00]

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

[commit-bot: I haz the power, 2015-01-30 18:40:01]

Try jobs failed on following builders:
  android_dbg_tests_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_dbg_tes...)

[Raymond Toy, 2015-02-03 18:57:20]

The CQ bit was checked by rtoy@chromium.org

[commit-bot: I haz the power, 2015-02-03 18:58:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885183002/1

[commit-bot: I haz the power, 2015-02-03 19:57:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-03 19:58:33]

Patchset 1 (id:??) landed as
https://crrev.com/10ab4e95843c5a4759282d695a9680ee9085dd01
Cr-Commit-Position: refs/heads/master@{#314390}