Add a treeChange type to Automation

ui/accessibility/ax_tree_unittest.cc

Index: ui/accessibility/ax_tree_unittest.cc
diff --git a/ui/accessibility/ax_tree_unittest.cc b/ui/accessibility/ax_tree_unittest.cc
index 94fc9b80b3b758f43348a620e71fb06d545cff8e..27f8dae879b11314073206ada2dc8ce948d71373 100644
--- a/ui/accessibility/ax_tree_unittest.cc
+++ b/ui/accessibility/ax_tree_unittest.cc
@@ -23,6 +23,9 @@ class FakeAXTreeDelegate : public AXTreeDelegate {
       : tree_data_changed_(false),
         root_changed_(false) {}
 
+  void OnNodeDataWillChange(AXTree* tree,
+                            const AXNodeData& old_node_data,
+                            const AXNodeData& new_node_data) override {}
   void OnTreeDataChanged(AXTree* tree) override {
     tree_data_changed_ = true;
   }