Optimize BlinkAXTreeSource by adding freeze/thaw for things like root, focus.

content/renderer/accessibility/render_accessibility_impl.cc

 // Copyright (c) 2012 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 "content/renderer/accessibility/render_accessibility_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <queue>
@@ skipping 40 matching lines @@
     AXContentTreeUpdate* response) {
   DCHECK(render_frame);
   DCHECK(response);
   if (!render_frame->GetWebFrame())
     return;
 
   WebDocument document = render_frame->GetWebFrame()->document();
   WebScopedAXContext context(document);
   BlinkAXTreeSource tree_source(render_frame);
   tree_source.SetRoot(context.root());
+  ScopedFreezeBlinkAXTreeSource freeze(&tree_source);
   BlinkAXTreeSerializer serializer(&tree_source);
   serializer.set_max_node_count(kMaxSnapshotNodeCount);
   serializer.SerializeChanges(context.root(), response);
 }
 
 RenderAccessibilityImpl::RenderAccessibilityImpl(RenderFrameImpl* render_frame)
     : RenderFrameObserver(render_frame),
       render_frame_(render_frame),
       tree_source_(render_frame),
       serializer_(&tree_source_),
@@ skipping 166 matching lines @@
 int RenderAccessibilityImpl::GenerateAXID() {
   WebAXObject root = tree_source_.GetRoot();
   return root.generateAXID();
 }
 
 void RenderAccessibilityImpl::SetPdfTreeSource(
     RenderAccessibilityImpl::PdfAXTreeSource* pdf_tree_source) {
   pdf_tree_source_ = pdf_tree_source;
   pdf_serializer_.reset(new PdfAXTreeSerializer(pdf_tree_source_));
 
+  ScopedFreezeBlinkAXTreeSource freeze(&tree_source_);
   WebAXObject root = tree_source_.GetRoot();
   if (!root.updateLayoutAndCheckValidity())
     return;
 
   std::queue<WebAXObject> objs_to_explore;
   objs_to_explore.push(root);
   while (objs_to_explore.size()) {
     WebAXObject obj = objs_to_explore.front();
     objs_to_explore.pop();
 
@@ skipping 51 matching lines @@
     WebAXObject obj = document.accessibilityObjectFromID(event.id);
 
     // Make sure the object still exists.
     if (!obj.updateLayoutAndCheckValidity())
       continue;
 
     // If it's ignored, find the first ancestor that's not ignored.
     while (!obj.isDetached() && obj.accessibilityIsIgnored())
       obj = obj.parentObject();
 
+    ScopedFreezeBlinkAXTreeSource freeze(&tree_source_);
+
     // Make sure it's a descendant of our root node - exceptions include the
     // scroll area that's the parent of the main document (we ignore it), and
     // possibly nodes attached to a different document.
     if (!tree_source_.IsInTree(obj))
       continue;
 
     AccessibilityHostMsg_EventParams event_msg;
     event_msg.event_type = event.event_type;
     event_msg.id = event.id;
     if (!serializer_.SerializeChanges(obj, &event_msg.update)) {
@@ skipping 22 matching lines @@
   reset_token_ = 0;
 
   if (had_layout_complete_messages)
     SendLocationChanges();
 }
 
 void RenderAccessibilityImpl::SendLocationChanges() {
   std::vector<AccessibilityHostMsg_LocationChangeParams> messages;
 
   // Update layout on the root of the tree.
+  ScopedFreezeBlinkAXTreeSource freeze(&tree_source_);
   WebAXObject root = tree_source_.GetRoot();
   if (!root.updateLayoutAndCheckValidity())
     return;
 
   // Do a breadth-first explore of the whole blink AX tree.
   base::hash_map<int, gfx::RectF> new_locations;
   std::queue<WebAXObject> objs_to_explore;
   objs_to_explore.push(root);
   while (objs_to_explore.size()) {
     WebAXObject obj = objs_to_explore.front();
@@ skipping 64 matching lines @@
     return;
 
   WebAXObject obj = root_obj.hitTest(point);
   if (obj.isDetached())
     return;
 
   // If the object that was hit has a child frame, we have to send a
   // message back to the browser to do the hit test in the child frame,
   // recursively.
   AXContentNodeData data;
+  ScopedFreezeBlinkAXTreeSource freeze(&tree_source_);
   tree_source_.SerializeNode(obj, &data);
   if (data.HasContentIntAttribute(AX_CONTENT_ATTR_CHILD_ROUTING_ID) ||
       data.HasContentIntAttribute(
           AX_CONTENT_ATTR_CHILD_BROWSER_PLUGIN_INSTANCE_ID)) {
     Send(new AccessibilityHostMsg_ChildFrameHitTestResult(routing_id(), point,
                                                           obj.axID()));
     return;
   }
 
   // Otherwise, send a HOVER event on the node that was hit.
   HandleAXEvent(obj, ui::AX_EVENT_HOVER);
 }
 
 void RenderAccessibilityImpl::OnSetAccessibilityFocus(int acc_obj_id) {
+  ScopedFreezeBlinkAXTreeSource freeze(&tree_source_);
   if (tree_source_.accessibility_focus_id() == acc_obj_id)
     return;
 
   tree_source_.set_accessibility_focus_id(acc_obj_id);
 
   const WebDocument& document = GetMainDocument();
   if (document.isNull())
     return;
 
   WebAXObject obj = document.accessibilityObjectFromID(acc_obj_id);
@@ skipping 204 matching lines @@
       size_t new_count = pdf_update.nodes.size();
       update->nodes.resize(old_count + new_count);
       for (size_t i = 0; i < new_count; ++i)
         update->nodes[old_count + i] = pdf_update.nodes[i];
       break;
     }
   }
 }
 
 }  // namespace content