[Sync] Implement keystore migration support.

sync/protocol/client_debug_info.proto

 // 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.
 //
 // Common sync protocol for encrypted data.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 option retain_unknown_fields = true;
@@ skipping 44 matching lines @@
 
     // |STOP_SYNCING_PERMANENTLY| event should never be seen by the server in
     // the absence of bugs.
     STOP_SYNCING_PERMANENTLY = 6; // Server sent stop syncing permanently.
 
     ENCRYPTED_TYPES_CHANGED = 9; // Set of encrypted types has changed.
     ENCRYPTION_COMPLETE = 7; // Client has finished encrypting all data.
     ACTIONABLE_ERROR = 8; // Client received an actionable error.
     BOOTSTRAP_TOKEN_UPDATED = 9;  // A new cryptographer bootstrap token was
                                   // generated.
-    PASSPHRASE_STATE_CHANGED = 10;  // The encryption passphrase state changed.
+    PASSPHRASE_TYPE_CHANGED = 10;  // The encryption passphrase state changed.
     KEYSTORE_TOKEN_UPDATED = 11;  // A new keystore encryption token was
                                   // persisted.
   }
   // In a given |DebugEventInfo| only one of the following would be set.
   optional EventType type = 1;
 
   optional SyncCycleCompletedEventInfo sync_cycle_completed_event_info = 2;
 
   // Datatype that caused the nudge.
   optional int32 nudging_datatype = 3;
 
   // Datatypes that were notified from server.
   repeated int32 datatypes_notified_from_server = 4;
 }
 
 message DebugInfo {
   repeated DebugEventInfo events = 1;
 
   // Whether cryptographer is ready to encrypt and decrypt data.
   optional bool cryptographer_ready = 2;
 
   // Cryptographer has pending keys which indicates the correct passphrase
   // has not been provided yet.
   optional bool cryptographer_has_pending_keys = 3;
 
   // Indicates client has dropped some events to save bandwidth.
   optional bool events_dropped = 4;
 }