sync: Remove dead code related to ClearUserData

sync/internal_api/public/sync_manager.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.
 
 #ifndef SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_
 #define SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 201 matching lines @@
      *     notifications are enabled.
      */
     // function getNotificationState(callback);
 
     virtual void OnInitializationComplete(
         const WeakHandle<JsBackend>& js_backend,
         const WeakHandle<DataTypeDebugInfoListener>& debug_info_listener,
         bool success,
         ModelTypeSet restored_types) = 0;
 
-    // We are no longer permitted to communicate with the server. Sync should
-    // be disabled and state cleaned up at once.  This can happen for a number
-    // of reasons, e.g. swapping from a test instance to production, or a
-    // global stop syncing operation has wiped the store.
-    virtual void OnStopSyncingPermanently() = 0;
-
     virtual void OnActionableError(
         const SyncProtocolError& sync_protocol_error) = 0;
 
    protected:
     virtual ~Observer();
   };
 
   SyncManager();
   virtual ~SyncManager();
 
@@ skipping 137 matching lines @@
   // Returns the SyncManager's encryption handler.
   virtual SyncEncryptionHandler* GetEncryptionHandler() = 0;
 
   // Ask the SyncManager to fetch updates for the given types.
   virtual void RefreshTypes(ModelTypeSet types) = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_