sync: Remove ClearUserData command.

sync/protocol/get_updates_caller_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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 option retain_unknown_fields = true;
 
 package sync_pb;
 
 message GetUpdatesCallerInfo {
   enum GetUpdatesSource {
     UNKNOWN = 0;  // The source was not set by the caller.
     FIRST_UPDATE = 1;  // First request after browser restart.  Not to
                        // be confused with "NEW_CLIENT".
     LOCAL = 2;  // The source of the update was a local change.
     NOTIFICATION = 3;  // The source of the update was a p2p notification.
     PERIODIC = 4;  // The source of the update was periodic polling.
     SYNC_CYCLE_CONTINUATION = 5;  // The source of the update was a
                                   // continuation of a previous update.
-    CLEAR_PRIVATE_DATA = 6;       // Source is a call to remove all private data
+
+    // This value is deprecated and was never used in production.
+    // CLEAR_PRIVATE_DATA = 6;
+
     NEWLY_SUPPORTED_DATATYPE = 7;   // The client is in configuration mode
                                     // because it's syncing all datatypes, and
                                     // support for a new datatype was recently
                                     // released via a software auto-update.
     MIGRATION = 8;         // The client is in configuration mode because a
                            // MIGRATION_DONE error previously returned by the
                            // server necessitated resynchronization.
     NEW_CLIENT = 9;        // The client is in configuration mode because the
                            // user enabled sync for the first time.  Not to be
                            // confused with FIRST_UPDATE.
     RECONFIGURATION = 10;  // The client is in configuration mode because the
                            // user opted to sync a different set of datatypes.
     DATATYPE_REFRESH = 11;    // A datatype has requested a refresh. This is
                               // typically used when datatype's have custom
                               // sync UI, e.g. sessions.
   }
 
   required GetUpdatesSource source = 1;
 
   // True only if notifications were enabled for this GetUpdateMessage.
   optional bool notifications_enabled = 2;
 };