content: convert accessibility notifications to observer usage

content/public/browser/render_view_host_observer.h

Index: content/public/browser/render_view_host_observer.h
diff --git a/content/public/browser/render_view_host_observer.h b/content/public/browser/render_view_host_observer.h
index 932e71536230f9d87b7025a940726460b3147c06..b3101e55edbe1bdc103a8eb623202d5e3e658c1a 100644
--- a/content/public/browser/render_view_host_observer.h
+++ b/content/public/browser/render_view_host_observer.h
@@ -41,6 +41,10 @@ class CONTENT_EXPORT RenderViewHostObserver : public IPC::Listener,
   // Notifies that a navigation is starting.
   virtual void Navigate(const GURL& url);
 
+  // Accessibility notifications.
+  virtual void AccessibilityLayoutComplete();

[dmazzoni, 2013/02/08 15:55:21]

Perhaps a single method with an argument would be cleaner?

  OnAccessibilityNotification(AccessibilityNotification notification_type);

A reason I didn't do that before (one notification with the accessibility
notification enum in the details) was so I could use
WindowedNotificationObserver.

+  virtual void AccessibilityLoadComplete();
+
   // IPC::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;