Remove TabContents from TabStripModelObserver::TabDetachedAt.

BUG=107201
TEST=no visible change


Review URL: https://chromiumcodereview.appspot.com/11293205

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@167122 0039d316-1c4b-4281-b951-d872f2087c98
  DeleteTabContentsOnDestroyedObserver(TabContents* source,
                                       TabContents* tab_to_delete)
      : source_(source),
        tab_to_delete_(tab_to_delete) {
    registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
                   content::Source<WebContents>(source->web_contents()));
  }

  DeleteTabContentsOnDestroyedObserver(TabContents* source,
                                       TabContents* tab_to_delete)
      : source_(source),
        tab_to_delete_(tab_to_delete) {
    registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
                   content::Source<WebContents>(source->web_contents()));
  }
