CL fixing a race-condition during experimental popup extension API pop-up closure.  The dismissal notification is sent asynchronously, after which the pop-up is entirely destructed.  The ExtensionPopupHost now holds a reference to the pop-up, so that it can safely make use of it during ExtensionPopupHost::DispatchPopupClosedEvent.
CL fixing a race-condition during experimental popup extension API pop-up closure.  The dismissal notification is sent asynchronously, after which the pop-up is entirely destructed.  The ExtensionPopupHost now holds a reference to the pop-up, so that it can safely make use of it during ExtensionPopupHost::DispatchPopupClosedEvent.

BUG=None
TEST=None
Review URL: http://codereview.chromium.org/1512002

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@43051 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser