Remove ourselves as a message loop observer in the tabstrip destructor to catch the case when the user closes the last tab in a tabstrip.  In this case, we add ourselves as a message loop observer and never get a chance to remove ourselves before the tabstrip is destroyed.
Remove ourselves as a message loop observer in the tabstrip destructor to catch the case when the user closes the last tab in a tabstrip.  In this case, we add ourselves as a message loop observer and never get a chance to remove ourselves before the tabstrip is destroyed.

BUG=14648
TEST=Open a new window and press the close button on the tab.  The browser should not crash.
Review URL: http://codereview.chromium.org/140006

git-svn-id: http://src.chromium.org/svn/trunk/src@18843 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 63475c8605a6ac4c7cfc2157480ced482585ce90
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser