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
int TabStripModel::GetIndexOfWebContents(const WebContents* contents) const {
  for (size_t i = 0; i < contents_data_.size(); ++i) {
    if (contents_data_[i]->contents == contents)
      return i;
  }
  return kNoTab;
}

int TabStripModel::GetIndexOfWebContents(const WebContents* contents) const {
  for (size_t i = 0; i < contents_data_.size(); ++i) {
    if (contents_data_[i]->contents == contents)
      return i;
  }
  return kNoTab;
}
