Add a treeChange type to Automation

ui/accessibility/ax_tree.cc

 // 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.
 
 #include "ui/accessibility/ax_tree.h"
 
 #include <stddef.h>
 
 #include <set>
 
@@ skipping 162 matching lines @@
   // This method updates one node in the tree based on serialized data
   // received in an AXTreeUpdate. See AXTreeUpdate for pre and post
   // conditions.
 
   // Look up the node by id. If it's not found, then either the root
   // of the tree is being swapped, or we're out of sync with the source
   // and this is a serious error.
   AXNode* node = GetFromId(src.id);
   if (node) {
     update_state->pending_nodes.erase(node);
+    if (delegate_)
+      delegate_->OnNodeDataWillChange(node->data(), src);
     node->SetData(src);
   } else {
     if (src.role != AX_ROLE_ROOT_WEB_AREA &&
         src.role != AX_ROLE_DESKTOP) {
       error_ = base::StringPrintf(
           "%d is not in the tree and not the new root", src.id);
       return false;
     }
     if (update_state->new_root) {
       error_ = "Tree update contains two new roots";
@@ skipping 112 matching lines @@
       update_state->pending_nodes.insert(child);
       update_state->new_nodes.insert(child);
     }
     new_children->push_back(child);
   }
 
   return success;
 }
 
 }  // namespace ui