sync: Remove ClearUserData command.

sync/protocol/sync.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.
 //
 // Sync protocol for communication between sync client and server.
 
 // Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
 // any fields in this file.
 
 syntax = "proto2";
@@ skipping 437 matching lines @@
 
   // Whether to create the mobile bookmarks folder if it's not
   // already created.  Should be set to true only by mobile clients.
   optional bool create_mobile_bookmarks_folder = 1000 [default = false];
 };
 
 message AuthenticateMessage {
   required string auth_token = 1;
 };
 
-// This message is sent to the server to clear data.  An asynchronous
-// response is returned to the client indicating that the server has received
-// the request and has begun to clear data.
-message ClearUserDataMessage {
-}
-
-message ClearUserDataResponse {
-}
-
 message ClientToServerMessage {
   required string share = 1;
   optional int32 protocol_version = 2 [default = 31];
   enum Contents {
     COMMIT = 1;
     GET_UPDATES = 2;
     AUTHENTICATE = 3;
     CLEAR_DATA = 4;
   }
 
   required Contents message_contents = 3;
   optional CommitMessage commit = 4;
   optional GetUpdatesMessage get_updates = 5;
   optional AuthenticateMessage authenticate = 6;
-  // Request to clear all Chromium data from the server
-  optional ClearUserDataMessage clear_user_data = 9;
+
+  // Request to clear all Chromium data from the server.
+  // DEPRECATED - this field was never used in production.
+  // optional ClearUserDataMessage clear_user_data = 9;
 
   optional string store_birthday = 7; // Opaque store ID; if it changes, duck!
   // The client sets this if it detects a sync issue. The server will tell it
   // if it should perform a refresh.
   optional bool sync_problem_detected = 8 [default = false];
 
   // Client side state information for debugging purpose.
   // This is only sent on the first getupdates of every sync cycle,
   // as an optimization to save bandwidth.
   optional DebugInfo debug_info = 10;
@@ skipping 132 matching lines @@
   required double target_utilization = 2;
   required double measure_interval_max = 3;
   required double measure_interval_min = 4;
   required double observation_window = 5;
 };
 
 message ClientToServerResponse {
   optional CommitResponse commit = 1;
   optional GetUpdatesResponse get_updates = 2;
   optional AuthenticateResponse authenticate = 3;
-  optional ClearUserDataResponse clear_user_data = 9;
+  // DEPRECATED - this field was never used in production.
+  // optional ClearUserDataResponse clear_user_data = 9;
   optional GetUpdatesMetadataResponse stream_metadata = 10;
   // If GetUpdatesStreamingResponse is contained in the ClientToServerResponse,
   // none of the other fields (error_code and etc) will be set.
   optional GetUpdatesStreamingResponse stream_data = 11;
 
   message Error {
     optional SyncEnums.ErrorType error_type = 1 [default = UNKNOWN];
     optional string error_description       = 2;
     optional string url                     = 3;
     optional SyncEnums.Action action        = 4 [default = UNKNOWN_ACTION];
@@ skipping 22 matching lines @@
   optional string store_birthday = 6;
 
   optional ClientCommand client_command = 7;
   optional ProfilingData profiling_data = 8;
 
   // The data types whose storage has been migrated.  Present when the value of
   // error_code is MIGRATION_DONE.
   repeated int32 migrated_data_type_id = 12;
 };