Add a treeChange type to Automation

ui/accessibility/ax_tree.h

 // Copyright 2013 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_ACCESSIBILITY_AX_TREE_H_
 #define UI_ACCESSIBILITY_AX_TREE_H_
 
 #include <stdint.h>
 
 #include <set>
@@ skipping 23 matching lines @@
 // In addition, one additional notification is fired at the end of an
 // atomic update, and it provides a vector of nodes that were added or
 // changed, for final postprocessing:
 //   OnAtomicUpdateFinished
 //
 class AX_EXPORT AXTreeDelegate {
  public:
   AXTreeDelegate();
   virtual ~AXTreeDelegate();
 
+  // Called before a node's data gets updated.
+  virtual void OnNodeDataWillChange(const AXNodeData& old_node_data,

[dmazzoni, 2016/02/19 23:20:23]

For completeness I'd pass the AXTree* and AXNode* here to match the other
interfaces

+                                    const AXNodeData& new_node_data) = 0;
+
   // Called when tree data changes.
   virtual void OnTreeDataChanged(AXTree* tree) = 0;
 
   // Called just before a node is deleted. Its id and data will be valid,
   // but its links to parents and children are invalid. This is called
   // in the middle of an update, the tree may be in an invalid state!
   virtual void OnNodeWillBeDeleted(AXTree* tree, AXNode* node) = 0;
 
   // Same as OnNodeWillBeDeleted, but only called once for an entire subtree.
   // This is called in the middle of an update, the tree may be in an
@@ skipping 105 matching lines @@
   AXTreeDelegate* delegate_;
   AXNode* root_;
   base::hash_map<int32_t, AXNode*> id_map_;
   std::string error_;
   AXTreeData data_;
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_AX_TREE_H_