Before object destruction, make sure that its select dialogs are told that we

      are gone so that they don't try and call back to us. This bug was reproducible
on extensions, but similar occurences were found in code auditing.

BUG=77349
TEST=None
Review URL: http://codereview.chromium.org/6747007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@79507 0039d316-1c4b-4281-b951-d872f2087c98