evaluateScriptInMainWorld() should check if the target context exists before evaluating a script

evaluateScriptInMainWorld() should check if the target context exists before evaluating a script

This is a speculative fix of bug 393137 (I cannot reproduce it).

It's possible that evaluateScriptInMainWorld() is called in a state where toV8Context(m_frame, mainWorld()) returns NULL. For example, this can happen when the m_frame is already detached from the window object (but I don't figure out the exact call path that causes the issue).

Either way, evaluateScriptInMainWorld() should check if the target context exists or not before starting evaluating a script. This CL makes the change.

BUG=393137
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178047

[haraken, 2014-07-14 09:43:26]

PTAL

[dcarney, 2014-07-14 09:53:37]

lgtm

[haraken, 2014-07-14 09:54:19]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2014-07-14 09:55:16]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/haraken@chromium.org/388913004/1

[commit-bot: I haz the power, 2014-07-14 10:57:10]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)

[commit-bot: I haz the power, 2014-07-14 11:55:48]

Change committed as 178047