sync: Move migration signal out of snapshot

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 210 matching lines @@
 
     // 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;
 
+    virtual void OnMigrationRequested(ModelTypeSet types) = 0;
+
    protected:
     virtual ~Observer();
   };
 
   SyncManager();
   virtual ~SyncManager();
 
   // Initialize the sync manager.  |database_location| specifies the path of
   // the directory in which to locate a sqlite repository storing the syncer
   // backend state. Initialization will open the database, or create it if it
@@ skipping 134 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_