Fix a couple of (likely rare) crashers that can happen if a tab is closed right as it's about to display a JS modal dialog.
Fix a couple of (likely rare) crashers that can happen if a tab is closed right as it's about to display a JS modal dialog.

I don't know how these would be triggered in the field.  I ran into them through misuse of the current API (trying to pass in a NULL WebContents).

Review URL: http://codereview.chromium.org/62079

git-svn-id: http://src.chromium.org/svn/trunk/src@13203 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: abd607fc7254ca7085948f4ac5b0bc0bbe98adde
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