[Sync] Introduce ModelError for USS error handling.

components/sync/model/model_type_store.h

Index: components/sync/model/model_type_store.h
diff --git a/components/sync/model/model_type_store.h b/components/sync/model/model_type_store.h
index 02448ea0c0fb30d2c79a4e555b27167368dfd91c..dd361f390e8ae4b5d060702dc28dad5abf516b7d 100644
--- a/components/sync/model/model_type_store.h
+++ b/components/sync/model/model_type_store.h
@@ -14,7 +14,7 @@
 #include "components/sync/base/model_type.h"
 #include "components/sync/model/metadata_batch.h"
 #include "components/sync/model/metadata_change_list.h"
-#include "components/sync/model/sync_error.h"
+#include "components/sync/model/model_error.h"
 
 namespace base {
 class SequencedTaskRunner;
@@ -119,7 +119,7 @@ class ModelTypeStore {
   typedef base::Callback<void(Result result,
                               std::unique_ptr<RecordList> data_records)>
       ReadAllDataCallback;
-  typedef base::Callback<void(SyncError sync_error,
+  typedef base::Callback<void(ModelError error,
                               std::unique_ptr<MetadataBatch> metadata_batch)>
       ReadMetadataCallback;