Add a treeChange type to Automation

ui/accessibility/ax_tree.h

Index: ui/accessibility/ax_tree.h
diff --git a/ui/accessibility/ax_tree.h b/ui/accessibility/ax_tree.h
index 62b0709fc35aaa9f4d25f0a14c5c71699727e355..3f0868f15309b0d35bcdf58dda3bf8eb44499c79 100644
--- a/ui/accessibility/ax_tree.h
+++ b/ui/accessibility/ax_tree.h
@@ -41,6 +41,10 @@ class AX_EXPORT AXTreeDelegate {
   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;