Remove most remaining sync/notifier dependencies

sync/notifier/invalidator.h

 // Copyright 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.
 //
 // Interface to the invalidator, which is an object that receives
 // invalidations for registered object IDs. The corresponding
 // InvalidationHandler is notifier when such an event occurs.
 
 #ifndef SYNC_NOTIFIER_INVALIDATOR_H_
 #define SYNC_NOTIFIER_INVALIDATOR_H_
 
 #include <string>
 
+#include "base/callback.h"
 #include "sync/base/sync_export.h"
 #include "sync/internal_api/public/base/invalidator_state.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/notifier/invalidation_util.h"
 
 namespace syncer {
 class InvalidationHandler;
 
 class SYNC_EXPORT Invalidator {
  public:
-  Invalidator() {}
-  virtual ~Invalidator() {}
+  Invalidator();
+  virtual ~Invalidator();
 
   // Clients should follow the pattern below:
   //
   // When starting the client:
   //
   //   invalidator->RegisterHandler(client_handler);
   //
   // When the set of IDs to register changes for the client during its lifetime
   // (i.e., between calls to RegisterHandler(client_handler) and
   // UnregisterHandler(client_handler):
@@ skipping 43 matching lines @@
   virtual void UpdateCredentials(
       const std::string& email, const std::string& token) = 0;
 
   // Requests internal detailed status to be posted back to the callback.
   virtual void RequestDetailedStatus(
       base::Callback<void(const base::DictionaryValue&)> callback) const = 0;
 };
 }  // namespace syncer
 
 #endif  // SYNC_NOTIFIER_INVALIDATOR_H_