[Sync] Convert SyncSessionSnapshot to a copy-able class.

sync/internal_api/all_status.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.
 //
 // The AllStatus object watches various sync engine components and aggregates
 // the status of all of them into one place.
 
 #ifndef SYNC_INTERNAL_API_ALL_STATUS_H_
 #define SYNC_INTERNAL_API_ALL_STATUS_H_
 #pragma once
 
 #include <map>
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/lock.h"
 #include "sync/engine/syncer_types.h"
+#include "sync/engine/sync_engine_event.h"
 #include "sync/internal_api/sync_manager.h"
 #include "sync/syncable/model_type.h"
 
 namespace browser_sync {
 
 class ScopedStatusLock;
 struct ServerConnectionEvent;
 
 // TODO(rlarocque):
 // Most of this data ends up on the about:sync page.  But the page is only
@@ skipping 44 matching lines @@
  public:
   explicit ScopedStatusLock(AllStatus* allstatus);
   ~ScopedStatusLock();
  protected:
   AllStatus* allstatus_;
 };
 
 }  // namespace browser_sync
 
 #endif  // SYNC_INTERNAL_API_ALL_STATUS_H_