Add initial GTK web accessibility framework (new with valgrind fix).

content/browser/accessibility/browser_accessibility_manager_mac.mm

 // 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.
 
 #include "content/browser/accessibility/browser_accessibility_manager_mac.h"
 
 #import "base/logging.h"
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 #include "content/common/accessibility_messages.h"
 
@@ skipping 11 matching lines @@
     gfx::NativeView parent_window,
     const webkit_glue::WebAccessibility& src,
     BrowserAccessibilityDelegate* delegate,
     BrowserAccessibilityFactory* factory)
         : BrowserAccessibilityManager(parent_window, src, delegate, factory) {
 }
 
 void BrowserAccessibilityManagerMac::NotifyAccessibilityEvent(
     int type,
     BrowserAccessibility* node) {
+  BrowserAccessibilityCocoa* native_node = node->ToBrowserAccessibilityCocoa();
+  if (!native_node)
+    return;
+
   // Refer to AXObjectCache.mm (webkit).
   NSString* event_id = @"";
   switch (type) {
     case AccessibilityNotificationActiveDescendantChanged:
       if (node->role() == WebAccessibility::ROLE_TREE)
         event_id = NSAccessibilitySelectedRowsChangedNotification;
       else
         event_id = NSAccessibilityFocusedUIElementChangedNotification;
     case AccessibilityNotificationAlert:
       // Not used on Mac.
@@ skipping 49 matching lines @@
     case AccessibilityNotificationTextInserted:
       // Not used on Mac.
       return;
     case AccessibilityNotificationTextRemoved:
       // Not used on Mac.
       return;
     case AccessibilityNotificationValueChanged:
       event_id = NSAccessibilityValueChangedNotification;
       break;
   }
-  BrowserAccessibilityCocoa* native_node = node->toBrowserAccessibilityCocoa();
-  DCHECK(native_node);
   NSAccessibilityPostNotification(native_node, event_id);
 }