ui/base/models: Add empty() accessor to TreeNode class.

ui/base/models/tree_node_model.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_BASE_MODELS_TREE_NODE_MODEL_H_
 #define UI_BASE_MODELS_TREE_NODE_MODEL_H_
 #pragma once
 
 #include <algorithm>
 #include <vector>
@@ skipping 94 matching lines @@
   // Returns the parent node, or NULL if this is the root node.
   const NodeType* parent() const { return parent_; }
   NodeType* parent() { return parent_; }
 
   // Returns true if this is the root node.
   bool is_root() const { return parent_ == NULL; }
 
   // Returns the number of children.
   int child_count() const { return static_cast<int>(children_->size()); }
 
+  // Returns true if this node has no children.
+  bool empty() const { return children_.empty(); }
+
   // Returns the number of all nodes in the subtree rooted at this node,
   // including this node.
   int GetTotalNodeCount() const {
     int count = 1;  // Start with one to include the node itself.
     for (size_t i = 0; i < children_->size(); ++i)
       count += children_[i]->GetTotalNodeCount();
     return count;
   }
 
   // Returns the node at |index|.
@@ skipping 161 matching lines @@
 
   // The root.
   scoped_ptr<NodeType> root_;
 
   DISALLOW_COPY_AND_ASSIGN(TreeNodeModel);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_TREE_NODE_MODEL_H_