ui: Cleanup class/struct forward declarations

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 9746aff2d1ffc8eb094e56c8e16ca4d88c016ad5..07d1082d8273869ab228c40ddb3f969fcc7f4f6a 100644
--- a/components/sync/model/model_type_store.h
+++ b/components/sync/model/model_type_store.h
@@ -12,7 +12,9 @@
 #include "base/callback.h"
 #include "base/macros.h"
 #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"
 
 namespace base {
 class SequencedTaskRunner;
@@ -111,9 +113,8 @@ class ModelTypeStore {
   typedef base::Callback<void(Result result,
                               std::unique_ptr<RecordList> data_records)>
       ReadAllDataCallback;
-  typedef base::Callback<void(Result result,
-                              std::unique_ptr<RecordList> metadata_records,
-                              const std::string& global_metadata)>
+  typedef base::Callback<void(SyncError sync_error,
+                              std::unique_ptr<MetadataBatch> metadata_batch)>
       ReadMetadataCallback;
 
   // CreateStore takes |path| and |blocking_task_runner|. Here is how to get