Fixing a crash in RenderViewGone....

Fixing a crash in RenderViewGone.

If I start Chrome and shut it down quickly RenderViewHost
receives an IPC ViewHostMsg_RenderViewGone. We respond in
ExtensionHost::RenderViewGone by putting up an info bar on
the selected tab contents saying that an extension
crashed. 

Only problem is that ExtensionHost::GetBrowser() can
return NULL during startup and shutdown, as documented
in the function and so we should not try to put up the
Infobar if the browser is going away.

BUG=None
TEST=Open Chrome with extensions enabled and an extension
loaded and shut Chrome down as soon as it launches. It
should not crash. Might take a few trys to repro.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=19986

[Paweł Hajdan Jr., 2009-07-06 17:59:44]

LGTM