Implement cancel() API on a Notification object so that script can cancel or ...

chrome/browser/notifications/notification_object_proxy.h

Index: chrome/browser/notifications/notification_object_proxy.h
===================================================================
--- chrome/browser/notifications/notification_object_proxy.h	(revision 30967)
+++ chrome/browser/notifications/notification_object_proxy.h	(working copy)
@@ -31,9 +31,17 @@
   void Error();
 
   // To be called when the desktop notification is closed.  If closed by a
-  // user explicitly (as opposed to timeout), |by_user| should be true.
+  // user explicitly (as opposed to timeout/script), |by_user| should be true. q
   void Close(bool by_user);
 
+  // Compares two proxies by ids to decide if they are equal.
+  bool IsSame(const NotificationObjectProxy& other) const {
+    return (notification_id_ == other.notification_id_ &&
+            route_id_ == other.route_id_ &&
+            process_id_ == other.process_id_ &&
+            worker_ == other.worker_);
+  }
+
  private:
   // Called on UI thread to schedule a message for sending.
   void DeliverMessage(IPC::Message* message);