Implement new invalidations ack tracking system

chrome/browser/extensions/api/push_messaging/push_messaging_invalidation_handler.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_PUSH_MESSAGING_INVALIDATION_HANDLER_H_
 #define CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_PUSH_MESSAGING_INVALIDATION_HANDLER_H_
 
+#include <map>
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/threading/thread_checker.h"
 #include "chrome/browser/extensions/api/push_messaging/push_messaging_invalidation_mapper.h"
 #include "sync/notifier/invalidation_handler.h"
+#include "sync/notifier/invalidation_util.h"
 
 namespace invalidation {
 class InvalidationService;
 }
 
 namespace extensions {
 
 class PushMessagingInvalidationHandlerDelegate;
 
 // This class maps extension IDs to the corresponding object IDs, manages
@@ skipping 27 matching lines @@
   }
 
  private:
   void UpdateRegistrations();
 
   base::ThreadChecker thread_checker_;
   invalidation::InvalidationService* const service_;
   std::set<std::string> registered_extensions_;
   syncer::ObjectIdSet suppressed_ids_;
   PushMessagingInvalidationHandlerDelegate* const delegate_;
+  std::map<invalidation::ObjectId,
+           int64,
+           syncer::ObjectIdLessThan> max_object_version_map_;
 
   DISALLOW_COPY_AND_ASSIGN(PushMessagingInvalidationHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_PUSH_MESSAGING_INVALIDATION_HANDLER_H_