Add initial GTK web accessibility framework (third attempt).

content/browser/accessibility/browser_accessibility_mac.h

Index: content/browser/accessibility/browser_accessibility_mac.h
===================================================================
--- content/browser/accessibility/browser_accessibility_mac.h	(revision 135807)
+++ content/browser/accessibility/browser_accessibility_mac.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -20,6 +20,7 @@
   // Implementation of BrowserAccessibility.
   virtual void PreInitialize() OVERRIDE;
   virtual void NativeReleaseReference() OVERRIDE;
+  virtual bool IsNative() const OVERRIDE;
 
   // Overrides from BrowserAccessibility.
   virtual void DetachTree(std::vector<BrowserAccessibility*>* nodes) OVERRIDE;