Use unique IDs for accessibility nodes on Android

ui/accessibility/platform/ax_platform_node.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_PLATFORM_AX_PLATFORM_NODE_H_
 #define UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_H_
 
 #include "build/build_config.h"
 #include "ui/accessibility/ax_enums.h"
 #include "ui/accessibility/ax_export.h"
@@ skipping 28 matching lines @@
  public:
   // Create an appropriate platform-specific instance. The delegate owns the
   // AXPlatformNode instance (or manages its lifecycle in some other way).
   static AXPlatformNode* Create(AXPlatformNodeDelegate* delegate);
 
   // Cast a gfx::NativeViewAccessible to an AXPlatformNode if it is one,
   // or return NULL if it's not an instance of this class.
   static AXPlatformNode* FromNativeViewAccessible(
       gfx::NativeViewAccessible accessible);
 
+  // Each platform accessibility object has a unique id that's guaranteed
+  // to be a positive number. (It's stored in an int32_t as opposed to
+  // uint32_t because some platforms want to negate it, so we want to ensure
+  // the range is below the signed int max.) This can be used when the
+  // id has to be unique across multiple frames, since node ids are
+  // only unique within one tree.
+  static int32_t GetNextUniqueId();
+
   // Call Destroy rather than deleting this, because the subclass may
   // use reference counting.
-  virtual void Destroy() = 0;
+  virtual void Destroy();
 
   // Get the platform-specific accessible object type for this instance.
   // On some platforms this is just a type cast, on others it may be a
   // wrapper object or handle.
   virtual gfx::NativeViewAccessible GetNativeViewAccessible() = 0;
 
   // Fire a platform-specific notification that an event has occurred on
   // this object.
   virtual void NotifyAccessibilityEvent(ui::AXEvent event_type) = 0;
 
   // Return this object's delegate.
   virtual AXPlatformNodeDelegate* GetDelegate() const = 0;
 
  protected:
   AXPlatformNode();
   virtual ~AXPlatformNode();
+
+  AXPlatformNode* GetFromUniqueId(int32_t unique_id);
+
+  int32_t unique_id_;
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_H_