Add OVERRIDE to ui::TreeModelObserver overridden methods.

BUG=None
TEST=None

R=sky@chromium.org

Review URL: http://codereview.chromium.org/7046093

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@88827 0039d316-1c4b-4281-b951-d872f2087c98
void TreeView::DeleteRootItems() {
  HTREEITEM root = TreeView_GetRoot(tree_view_);
  if (root) {
    if (root_shown_) {
      RecursivelyDelete(GetNodeDetailsByTreeItem(root));
    } else {
      do {
        RecursivelyDelete(GetNodeDetailsByTreeItem(root));
      } while ((root = TreeView_GetRoot(tree_view_)));
    }
  }
}

void TreeView::DeleteRootItems() {
  HTREEITEM root = TreeView_GetRoot(tree_view_);
  if (root) {
    if (root_shown_) {
      RecursivelyDelete(GetNodeDetailsByTreeItem(root));
    } else {
      do {
        RecursivelyDelete(GetNodeDetailsByTreeItem(root));
      } while ((root = TreeView_GetRoot(tree_view_)));
    }
  }
}
