[Sync] Add sync api support for context changes

sync/api/sync_change.cc

 // 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.
 
 #include "sync/api/sync_change.h"
 
 #include <ostream>
 
 namespace syncer {
 
 SyncChange::SyncChange() : change_type_(ACTION_INVALID) {
 }
 
 SyncChange::SyncChange(
     const tracked_objects::Location& from_here,
     SyncChangeType change_type,
     const SyncData& sync_data)
     : location_(from_here),
       change_type_(change_type),
       sync_data_(sync_data) {
   DCHECK(IsValid());
 }
 
 SyncChange::~SyncChange() {}
 
 bool SyncChange::IsValid() const {
   if (change_type_ == ACTION_INVALID || !sync_data_.IsValid())
     return false;
 
+  // Context changes must not have valid specifics.
+  if (change_type_ == CONTEXT_UPDATE &&
+      GetModelTypeFromSpecifics(sync_data_.GetSpecifics()) != UNSPECIFIED) {
+    return false;
+  }
+
   // Data from the syncer must always have valid specifics.
   if (!sync_data_.IsLocal())
     return IsRealDataType(sync_data_.GetDataType());
 
   // Local changes must always have a tag and specify a valid datatype.
   if (sync_data_.GetTag().empty() ||
       !IsRealDataType(sync_data_.GetDataType())) {
     return false;
   }
 
@@ skipping 20 matching lines @@
 std::string SyncChange::ChangeTypeToString(SyncChangeType change_type) {
   switch (change_type) {
     case ACTION_INVALID:
       return "ACTION_INVALID";
     case ACTION_ADD:
       return "ACTION_ADD";
     case ACTION_UPDATE:
       return "ACTION_UPDATE";
     case ACTION_DELETE:
       return "ACTION_DELETE";
     default:

[maniscalco, 2014/03/31 23:59:16]

Needs to be updated?

[Nicolas Zea, 2014/04/02 18:34:36]

Woops, good catch, done.

       NOTREACHED();
   }
   return std::string();
 }
 
 std::string SyncChange::ToString() const {
   return "{ " + location_.ToString() + ", changeType: " +
       ChangeTypeToString(change_type_) + ", syncData: " +
       sync_data_.ToString() + "}";
 }
 
 void PrintTo(const SyncChange& sync_change, std::ostream* os) {
   *os << sync_change.ToString();
 }
 
 }  // namespace syncer