[Sync] Add sync api support for context changes

sync/api/sync_change_processor.cc

Index: sync/api/sync_change_processor.cc
diff --git a/sync/api/sync_change_processor.cc b/sync/api/sync_change_processor.cc
index 4a0607e07f4349d9f06818e36b2a5b579b95a73b..f6c268cda14f438699da78b553ac52f94c57ef55 100644
--- a/sync/api/sync_change_processor.cc
+++ b/sync/api/sync_change_processor.cc
@@ -10,4 +10,11 @@ SyncChangeProcessor::SyncChangeProcessor() {}
 
 SyncChangeProcessor::~SyncChangeProcessor() {}
 
+syncer::SyncError SyncChangeProcessor::UpdateDataTypeContext(
+    ModelType type,
+    const std::string& context) {
+  // Do nothing.
+  return syncer::SyncError();
+}
+
 }  // namespace syncer