Don't reenter Webkit, while it waits for outgoing sync calls to complete. Thi...

Don't reenter Webkit, while it waits for outgoing sync calls to complete. This
fixes bug http://code.google.com/p/chromium/issues/detail?id=4582, which is a crash in the renderer process, which occurs when the renderer receives a sync message requesting accessibility information from the browser, while it waits
for the PluginDestroyed sync call to unwind.

The ViewMsg_GetAccessibilityInfo has a timeout associated with it, which indicates that it is ok for the call to fail. We now turn off the unblock flag on the sync message which will ensure that it does not reenter Webkit in this scenario.

R=jcampan
Bug=4582
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=5927

[jcampan, 2008-11-24 19:10:04]

LGTM

Jay

[jam, 2008-11-25 20:58:59]

I think this change is risky.  Sure WebKit is not reentrant, but the problem
here isn't inside WebKit, it's inside the browser code, which we have control
over.

The WebKit code already gets reentered a lot when there are plugins, so I'm not
sure that the problem is there.  Do you have a reproducible scenario for this?