Mirror Windows implementation of CancelOnMessageLoopThread.

Mirror Windows implementation of CancelOnMessageLoopThread.

Before this change, there was a code path where the FilePathWatcher could have been canceled but the delegate_ was not set to NULL. At exit, the destructor would then call Cancel() which would try to post a task to the message loop. With this change, the delegate is correctly set to NULL when the MessageLoop is destroyed even if the FilePathWatcher itself has been canceled. This allows Cancel() from the destructor to do the right thing and not call into the MessageLoop.

This implementation matches the Windows version which does not crash.

BUG=83190
TEST=FilePathWatcherTest.*


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=97248

[dominich, 2011-08-17 19:19:55]

This should fix a fairly prevalent crasher by correctly setting the internal
state when the FilePathWatcher is canceled on the message loop thread.

[dmac, 2011-08-17 19:28:15]

On 2011/08/17 19:19:55, dominich wrote:
> This should fix a fairly prevalent crasher by correctly setting the internal
> state when the FilePathWatcher is canceled on the message loop thread.

Dominich, I'm not sure I understand what's going on here. Could you expand in
the description of this issue what you are doing and why?

[dominich, 2011-08-17 19:33:07]

Sorry, added much more detail. The callstack in the crash is pretty clear too.

[dmac, 2011-08-17 19:36:24]

On 2011/08/17 19:33:07, dominich wrote:
> Sorry, added much more detail. The callstack in the crash is pretty clear too.

Gotcha. LGTM

[commit-bot: I haz the power, 2011-08-18 00:26:26]

Change committed as 97248