Ignore V8's message handler that is invoked while we're initializing a window

Ignore V8's message handler that is invoked while we're initializing a window

messageHandlerInMainThread can be invoked while we're initializing a window (See stack traces in the bugs). In that half-baked situation, we don't have a valid context nor a valid world, so we should return immediately.

BUG=345014, 352179
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=169518

[haraken, 2014-03-18 18:10:10]

PTAL

[dcarney, 2014-03-18 20:22:03]

lgtm

[haraken, 2014-03-19 03:10:27]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2014-03-19 03:10:34]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/haraken@chromium.org/203123006/1

[commit-bot: I haz the power, 2014-03-19 04:13:13]

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

[commit-bot: I haz the power, 2014-03-19 04:13:14]

Try jobs failed on following builders:
  tryserver.blink on linux_blink_dbg

[haraken, 2014-03-19 04:20:36]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2014-03-19 04:20:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/haraken@chromium.org/203123006/1

[commit-bot: I haz the power, 2014-03-19 04:21:00]

Change committed as 169518