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
void BrowserEventRouter::TabChangedAt(TabContents* contents,
                                      int index,
                                      TabChangeType change_type) {
  TabUpdated(contents->web_contents(), false);
}

void BrowserEventRouter::TabChangedAt(TabContents* contents,
                                      int index,
                                      TabChangeType change_type) {
  TabUpdated(contents->web_contents(), false);
}
