Revert "aw: Disable ipc command buffer by default"

Revert "aw: Disable ipc command buffer by default"

Re-enable ipc based command buffer after fix for IO thread blocking
in r351894

BUG=509702
Committed: https://crrev.com/8a3a10e0cd0b1f893ff1bb3f577c18c93702c978
Cr-Commit-Position: refs/heads/master@{#351928}

[boliu, 2015-10-02 00:58:13]

err, just sending this through cq now

[boliu, 2015-10-02 00:58:28]

The CQ bit was checked by boliu@chromium.org

[commit-bot: I haz the power, 2015-10-02 00:58:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1380663004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1380663004/1

[commit-bot: I haz the power, 2015-10-02 01:03:58]

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

[commit-bot: I haz the power, 2015-10-02 01:03:59]

Try jobs failed on following builders:
  win_chromium_compile_dbg_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_comp...)
  win_chromium_x64_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[hush (inactive), 2015-10-02 01:05:27]

lgtm

[boliu, 2015-10-02 01:18:57]

The CQ bit was checked by boliu@chromium.org

[commit-bot: I haz the power, 2015-10-02 01:20:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1380663004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1380663004/1

[commit-bot: I haz the power, 2015-10-02 01:35:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-02 01:36:44]

Patchset 1 (id:??) landed as
https://crrev.com/8a3a10e0cd0b1f893ff1bb3f577c18c93702c978
Cr-Commit-Position: refs/heads/master@{#351928}