[Sync] Add plumbing of context from client to server

sync/engine/get_updates_processor_unittest.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/engine/get_updates_processor.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/stl_util.h"
 #include "sync/engine/get_updates_delegate.h"
 #include "sync/engine/update_handler.h"
@@ skipping 35 matching lines @@
   }
 
   void InitFakeUpdateResponse(sync_pb::GetUpdatesResponse* response) {
     ModelTypeSet types = enabled_types();
 
     for (ModelTypeSet::Iterator it = types.First(); it.Good(); it.Inc()) {
       sync_pb::DataTypeProgressMarker* marker =
           response->add_new_progress_marker();
       marker->set_data_type_id(GetSpecificsFieldNumberFromModelType(it.Get()));
       marker->set_token("foobarbaz");
+      sync_pb::DataTypeContext* context = response->add_context_mutations();
+      context->set_data_type_id(GetSpecificsFieldNumberFromModelType(it.Get()));
+      context->set_version(1);
+      context->set_context("context");
     }
 
     response->set_changes_remaining(0);
   }
 
   const UpdateHandler* GetHandler(ModelType type) {
     UpdateHandlerMap::iterator it = update_handler_map_.find(type);
     if (it == update_handler_map_.end())
       return NULL;
     return it->second;
@@ skipping 385 matching lines @@
 TEST_F(DownloadUpdatesDebugInfoTest, VerifyCopyOverwrites) {
   sync_pb::DebugInfo debug_info;
   AddDebugEvent();
   GetUpdatesProcessor::CopyClientDebugInfo(debug_info_getter(), &debug_info);
   EXPECT_EQ(1, debug_info.events_size());
   GetUpdatesProcessor::CopyClientDebugInfo(debug_info_getter(), &debug_info);
   EXPECT_EQ(1, debug_info.events_size());
 }
 
 }  // namespace syncer