Add a treeChange type to Automation

ui/accessibility/ax_tree.cc

Index: ui/accessibility/ax_tree.cc
diff --git a/ui/accessibility/ax_tree.cc b/ui/accessibility/ax_tree.cc
index bd879eaac441754030ef96bae00cdbec65370f2d..a3206632f71e56ac001816fd10976e396db0bc94 100644
--- a/ui/accessibility/ax_tree.cc
+++ b/ui/accessibility/ax_tree.cc
@@ -180,6 +180,8 @@ bool AXTree::UpdateNode(const AXNodeData& src,
   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 &&