sync: Add --enable-sync-sessions-v2 and necessary plumbing to use SessionsSyncManager.

chrome/browser/sync/sessions2/session_data_type_controller2.h

Index: chrome/browser/sync/sessions2/session_data_type_controller2.h
diff --git a/chrome/browser/sync/sessions2/session_data_type_controller2.h b/chrome/browser/sync/sessions2/session_data_type_controller2.h
new file mode 100644
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+++ b/chrome/browser/sync/sessions2/session_data_type_controller2.h
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+// Copyright 2013 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_SYNC_SESSIONS2_SESSION_DATA_TYPE_CONTROLLER2_H_
+#define CHROME_BROWSER_SYNC_SESSIONS2_SESSION_DATA_TYPE_CONTROLLER2_H_
+
+#include "chrome/browser/sync/glue/ui_data_type_controller.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+namespace browser_sync {
+
+// Overrides StartModels to avoid sync contention with sessions during
+// a session restore operation at startup.
+class SessionDataTypeController2 : public UIDataTypeController,
+                                   public content::NotificationObserver {
+ public:
+  SessionDataTypeController2(ProfileSyncComponentsFactory* factory,
+                             Profile* profile,
+                             ProfileSyncService* service);
+
+  // NotificationObserver interface.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+ protected:
+  virtual ~SessionDataTypeController2();
+  virtual bool StartModels() OVERRIDE;
+
+ private:
+  content::NotificationRegistrar notification_registrar_;
+  DISALLOW_COPY_AND_ASSIGN(SessionDataTypeController2);
+};
+
+}  // namespace browser_sync
+
+#endif  // CHROME_BROWSER_SYNC_SESSIONS2_SESSION_DATA_TYPE_CONTROLLER2_H_
+