[Sync] Add plumbing of context from client to server

sync/test/engine/mock_update_handler.cc

 // Copyright 2014 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.
 
 #include "sync/test/engine/mock_update_handler.h"
 
 #include "sync/internal_api/public/base/model_type.h"
 
 namespace syncer {
 
 MockUpdateHandler::MockUpdateHandler(ModelType type)
     : apply_updates_count_(0),
       passive_apply_updates_count_(0) {
   progress_marker_.set_data_type_id(GetSpecificsFieldNumberFromModelType(type));
   const std::string& token_str =
       std::string("Mock token: ") + std::string(ModelTypeToString(type));
   progress_marker_.set_token(token_str);
 }
 
 MockUpdateHandler::~MockUpdateHandler() {}
 
 void MockUpdateHandler::GetDownloadProgress(
       sync_pb::DataTypeProgressMarker* progress_marker) const {
   progress_marker->CopyFrom(progress_marker_);
 }
 
+void MockUpdateHandler::GetDataTypeContext(
+    sync_pb::DataTypeContext* context) const {
+  context->Clear();
+}
+
 void MockUpdateHandler::ProcessGetUpdatesResponse(
-      const sync_pb::DataTypeProgressMarker& progress_marker,
-      const SyncEntityList& applicable_updates,
-      sessions::StatusController* status) {
+    const sync_pb::DataTypeProgressMarker& progress_marker,
+    const sync_pb::DataTypeContext& mutated_context,
+    const SyncEntityList& applicable_updates,
+    sessions::StatusController* status) {
   progress_marker_.CopyFrom(progress_marker);
 }
 
 void MockUpdateHandler::ApplyUpdates(sessions::StatusController* status) {
   apply_updates_count_++;
 }
 
 void MockUpdateHandler::PassiveApplyUpdates(
     sessions::StatusController* status) {
   passive_apply_updates_count_++;
 }
 
 int MockUpdateHandler::GetApplyUpdatesCount() {
   return apply_updates_count_;
 }
 
 int MockUpdateHandler::GetPassiveApplyUpdatesCount() {
   return passive_apply_updates_count_;
 }
 
 }  // namespace syncer