One accessibility tree per frame.

content/browser/frame_host/frame_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 "content/browser/frame_host/frame_tree.h"
 
 #include <stddef.h>
 
 #include <queue>
 #include <utility>
@@ skipping 309 matching lines @@
     }
   }
 
   // If |node| was focused from a cross-process frame (i.e., via
   // window.focus()), tell its RenderFrame that it should focus.
   if (current_instance != source)
     node->current_frame_host()->SetFocusedFrame();
 
   focused_frame_tree_node_id_ = node->frame_tree_node_id();
   node->DidFocus();
+
+  // The accessibility tree data for the root of the frame tree keeps
+  // track of the focused frame too, so update that every time the
+  // focused frame changes.
+  root()->current_frame_host()->UpdateAXTreeData();
 }
 
 void FrameTree::SetFrameRemoveListener(
     const base::Callback<void(RenderFrameHost*)>& on_frame_removed) {
   on_frame_removed_ = on_frame_removed;
 }
 
 RenderViewHostImpl* FrameTree::CreateRenderViewHost(
     SiteInstance* site_instance,
     int32_t routing_id,
@@ skipping 158 matching lines @@
   // This is only used to set page-level focus in cross-process subframes, and
   // requests to set focus in main frame's SiteInstance are ignored.
   if (instance != root_manager->current_frame_host()->GetSiteInstance()) {
     RenderFrameProxyHost* proxy =
         root_manager->GetRenderFrameProxyHost(instance);
     proxy->Send(new InputMsg_SetFocus(proxy->GetRoutingID(), is_focused));
   }
 }
 
 }  // namespace content