Fixes possible deadlock between history and bookmarks. The deadlock

Fixes possible deadlock between history and bookmarks. The deadlock
would occur if you attempted to exit the browser, bookmarks hadn't
finished loading yet and HistoryBackend was waiting for bookmarks to
finish loading. In such a scenario bookmarks will never finish loading
because the UI thread is blocked waiting for history to finish
shutdown, but history can't finish because it's waiting for bookmarks.

I'm fixing it by signaling that bookmarks have finished loading, even
though that isn't entirely accurate in this case. It's possible that
could lead to nuking some favicons for bookmarks, but this scenario is
so rare that (IMO) it's not worth trying to handle specially.

BUG=96100
TEST=none
R=brettw@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=101076

[brettw, 2011-09-13 21:49:14]

LGTM

[sky, 2011-09-14 14:44:05]

Miranda, could you review the change to ProfileImpl.

Thanks,

  -Scott

[Miranda Callahan, 2011-09-14 14:48:27]

On 2011/09/14 14:44:05, sky wrote:
> Miranda, could you review the change to ProfileImpl.
> 
> Thanks,
> 
>   -Scott

ProfileImpl LGTM.