Initial support for native accessibility in ARC

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 CONTENT_BROWSER_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
-#define CONTENT_BROWSER_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
+#ifndef UI_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
+#define UI_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
 
 #include <map>
 #include <utility>
 
 #include "base/macros.h"
+#include "ui/accessibility/ax_export.h"
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
 }  // namespace base
 
-namespace content {
+namespace ui {
 
-// A class which generates a unique id given a process id and frame routing id.
-class AXTreeIDRegistry {
+// A class which generates a unique id.
+class AX_EXPORT AXTreeIDRegistry {
  public:
   using FrameID = std::pair<int, int>;
 
   using AXTreeID = int;
 
   static const AXTreeID kNoAXTreeID;
 
   // Get the single instance of this class.
   static AXTreeIDRegistry* GetInstance();
 
   // Obtains a unique id given a |process_id| and |routing_id|. Placeholder
   // for full implementation once out of process iframe accessibility finalizes.
   AXTreeID GetOrCreateAXTreeID(int process_id, int routing_id);
   FrameID GetFrameID(AXTreeID ax_tree_id);
   void RemoveAXTreeID(AXTreeID ax_tree_id);
 
+  // Create an id not associated with any process.
+  int CreateID();

[dmazzoni, 2017/02/09 01:18:09]

This is great.

Should we maybe use this for the Desktop tree? That'd probably be
a lot cleaner.

+
  private:
   friend struct base::DefaultSingletonTraits<AXTreeIDRegistry>;
 
   AXTreeIDRegistry();
   virtual ~AXTreeIDRegistry();
 
   // Tracks the current unique ax frame id.
   AXTreeID ax_tree_id_counter_;
 
   // Maps an accessibility tree to its frame via ids.
   std::map<AXTreeID, FrameID> ax_tree_to_frame_id_map_;
 
   // Maps frames to an accessibility tree via ids.
   std::map<FrameID, AXTreeID> frame_to_ax_tree_id_map_;
 
   DISALLOW_COPY_AND_ASSIGN(AXTreeIDRegistry);
 };
 
-}  // namespace content
+}  // namespace ui
 
-#endif  // CONTENT_BROWSER_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_
+#endif  // UI_ACCESSIBILITY_AX_TREE_ID_REGISTRY_H_