Re-land: Add a window property to associate RWHVA with its child AX tree ID

ui/accessibility/ax_tree_id_registry.h

 // Copyright 2014 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.
 
 #ifndef UI_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
 #define UI_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
 
 #include <map>
 #include <utility>
 
@@ skipping 16 matching lines @@
 //
 // The first form allows underlying instances to change but refer to the same
 // frame.
 // The second form allows this registry to track the object for later retrieval.
 class AX_EXPORT AXTreeIDRegistry {
  public:
   using FrameID = std::pair<int, int>;
 
   using AXTreeID = int;
 
-  static const AXTreeID kNoAXTreeID;
+  static constexpr AXTreeID kNoAXTreeID = -1;
 
   // Get the single instance of this class.
   static AXTreeIDRegistry* GetInstance();
 
   // Methods for FrameID ax tree id generation, and retrieval.
   AXTreeID GetOrCreateAXTreeID(int process_id, int routing_id);
   FrameID GetFrameID(AXTreeID ax_tree_id);
 
   // Retrieve an |AXHostDelegate|.
   AXHostDelegate* GetHostDelegate(AXTreeID ax_tree_id);
@@ skipping 22 matching lines @@
 
   // Maps an id to its host delegate.
   std::map<AXTreeID, AXHostDelegate*> id_to_host_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(AXTreeIDRegistry);
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_