[Sync] Services can now always assume processor exists.

components/sync/model_impl/shared_model_type_processor.cc

Index: components/sync/model_impl/shared_model_type_processor.cc
diff --git a/components/sync/model_impl/shared_model_type_processor.cc b/components/sync/model_impl/shared_model_type_processor.cc
index 9aac0477bc9a843eb2ce94cf5da9f6a738e76b62..06d0a1a99d0d9d035fe5fa8f2e370dbc6c41990a 100644
--- a/components/sync/model_impl/shared_model_type_processor.cc
+++ b/components/sync/model_impl/shared_model_type_processor.cc
@@ -106,7 +106,7 @@ void SharedModelTypeProcessor::ConnectIfReady() {
   std::unique_ptr<ActivationContext> activation_context;
 
   if (!start_error_.IsSet()) {
-    activation_context = base::WrapUnique(new ActivationContext);
+    activation_context = base::MakeUnique<ActivationContext>();
     activation_context->model_type_state = model_type_state_;
     activation_context->type_processor =
         base::MakeUnique<ModelTypeProcessorProxy>(
@@ -129,6 +129,7 @@ bool SharedModelTypeProcessor::IsConnected() const {
 
 void SharedModelTypeProcessor::DisableSync() {
   DCHECK(CalledOnValidThread());
+  DCHECK(is_metadata_loaded_);
   std::unique_ptr<MetadataChangeList> change_list =
       service_->CreateMetadataChangeList();
   for (auto it = entities_.begin(); it != entities_.end(); ++it) {
@@ -139,6 +140,10 @@ void SharedModelTypeProcessor::DisableSync() {
   service_->ApplySyncChanges(std::move(change_list), EntityChangeList());
 }
 
+bool SharedModelTypeProcessor::IsTrackingMetadata() {
+  return model_type_state_.initial_sync_done();
+}
+
 SyncError SharedModelTypeProcessor::CreateAndUploadError(
     const tracked_objects::Location& location,
     const std::string& message) {