sync: Move migration signal out of snapshot

chrome/browser/sync/glue/sync_backend_host_impl.h

 // 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_GLUE_SYNC_BACKEND_HOST_IMPL_H_
 #define CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_IMPL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 184 matching lines @@
       const std::string& token,
       syncer::BootstrapTokenType token_type);
 
   // For convenience, checks if initialization state is INITIALIZED.
   bool initialized() const { return initialized_; }
 
   // Let the front end handle the actionable error event.
   void HandleActionableErrorEventOnFrontendLoop(
       const syncer::SyncProtocolError& sync_error);
 
+  // Handle a migration request.
+  void HandleMigrationRequestedOnFrontendLoop(const syncer::ModelTypeSet types);
+
   // Checks if |passphrase| can be used to decrypt the cryptographer's pending
   // keys that were cached during NotifyPassphraseRequired. Returns true if
   // decryption was successful. Returns false otherwise. Must be called with a
   // non-empty pending keys cache.
   bool CheckPassphraseAgainstCachedPendingKeys(
       const std::string& passphrase) const;
 
   // Invoked when a passphrase is required to decrypt a set of Nigori keys,
   // or for encrypting. |reason| denotes why the passphrase was required.
   // |pending_keys| is a copy of the cryptographer's pending keys, that are
@@ skipping 98 matching lines @@
 
   base::WeakPtrFactory<SyncBackendHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHostImpl);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_IMPL_H_