libeven message-pump: Fix a particular case of nested message-loop runs.

libevent message-pump: Fix a particular case of nested message-loop runs.

If Quit() is called on the message-pump to terminate a nested loop, followed
by a call to Run() again to start another nested loop, in the same iteration
of the loop, then make sure it all works correctly.

We have this scenario with nested menus, modal dialogs, drag-drop etc. in
the browser UI. So this is a prerequisite fix to be able to use the
libevent based message-pump on Chrome OS (and get rid of glib dep).

BUG=240715
R=sky@chromium.org
TBR=darin@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266628

[sadrul, 2014-04-24 23:16:01]

+sky@ to load-balance review burden

[sky, 2014-04-25 14:31:38]

LGTM

[sadrul, 2014-04-28 19:30:13]

[ TBR'ing to darin@ ]

[sadrul, 2014-04-28 19:30:43]

Committed patchset #2 manually as r266628 (presubmit successful).

[darin (slow to review), 2014-04-28 19:32:13]

LGTM