Update V8 to version 4.6.55.

Update V8 to version 4.6.55.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/18967215..0c1ebe48

Please follow these instructions for assigning/CC'ing issues:
https://code.google.com/p/v8-wiki/wiki/TriagingIssues

Please close rolling in case of a roll revert:
https://v8-roll.appspot.com/

TBR=hablich@chromium.org,machenbach@chromium.org,yangguo@chromium.org,vogelheim@chromium.org

Committed: https://crrev.com/2384e9a19807d1e8fe240f0739bbfe8027a4a9aa
Cr-Commit-Position: refs/heads/master@{#342323}

[v8-autoroll, 2015-08-07 00:17:24]

The CQ bit was checked by v8-autoroll@chromium.org

[commit-bot: I haz the power, 2015-08-07 00:19:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1281683002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1281683002/1

[commit-bot: I haz the power, 2015-08-07 02:10:14]

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

[commit-bot: I haz the power, 2015-08-07 02:10:15]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Michael Achenbach, 2015-08-07 06:41:42]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-08-07 06:41:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1281683002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1281683002/1

[commit-bot: I haz the power, 2015-08-07 08:22:42]

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

[commit-bot: I haz the power, 2015-08-07 08:22:43]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Michael Achenbach, 2015-08-07 08:30:33]

Broken CQ - the GPU test failures are in HEAD and the CQ makes a false
rejection.

[Michael Achenbach, 2015-08-07 08:31:21]

On 2015/08/07 08:30:33, Michael Achenbach (OOO) wrote:
> Broken CQ - the GPU test failures are in HEAD and the CQ makes a false
> rejection.

Maybe it's now taken care of with
https://chromium.googlesource.com/chromium/src/+/c3bde8128e5b2b67cbdb5b7df49b...

[Michael Achenbach, 2015-08-07 08:32:07]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-08-07 08:32:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1281683002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1281683002/1

[commit-bot: I haz the power, 2015-08-07 09:08:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-07 09:09:49]

Patchset 1 (id:??) landed as
https://crrev.com/2384e9a19807d1e8fe240f0739bbfe8027a4a9aa
Cr-Commit-Position: refs/heads/master@{#342323}