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

ui/base/models/tree_node_iterator.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_ITERATOR_H_
 #define UI_BASE_MODELS_TREE_NODE_ITERATOR_H_
 #pragma once
 
 #include <stack>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 
 namespace ui {
 
 // Iterator that iterates over the descendants of a node. The iteration does
 // not include the node itself, only the descendants. The following illustrates
 // typical usage:
 // while (iterator.has_next()) {
 //   Node* node = iterator.Next();
 //   // do something with node.
 // }
 template <class NodeType>
 class TreeNodeIterator {
  public:
   explicit TreeNodeIterator(NodeType* node) {
-    if (node->child_count() > 0)
+    if (!node->empty())
       positions_.push(Position<NodeType>(node, 0));
   }
 
   // Returns true if there are more descendants.
   bool has_next() const { return !positions_.empty(); }
 
   // Returns the next descendant.
   NodeType* Next() {
     if (!has_next()) {
       NOTREACHED();
@@ skipping 28 matching lines @@
   };
 
   std::stack<Position<NodeType> > positions_;
 
   DISALLOW_COPY_AND_ASSIGN(TreeNodeIterator);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_TREE_NODE_ITERATOR_H_