[Sync] Prepend global metadata key with model type prefix

components/sync/model_impl/model_type_store_impl.h

Index: components/sync/model_impl/model_type_store_impl.h
diff --git a/components/sync/model_impl/model_type_store_impl.h b/components/sync/model_impl/model_type_store_impl.h
index 57bb9807d4fd44b9dafa0d4e64e97477f171f1ed..1810afc611779135617bd37e9e843c3fb3ae9049 100644
--- a/components/sync/model_impl/model_type_store_impl.h
+++ b/components/sync/model_impl/model_type_store_impl.h
@@ -30,11 +30,12 @@ class ModelTypeStoreImpl : public ModelTypeStore, public base::NonThreadSafe {
   ~ModelTypeStoreImpl() override;
 
   static void CreateStore(
-      const ModelType type,
+      ModelType type,
       const std::string& path,
       scoped_refptr<base::SequencedTaskRunner> blocking_task_runner,
       const InitCallback& callback);
-  static void CreateInMemoryStoreForTest(const InitCallback& callback);
+  static void CreateInMemoryStoreForTest(ModelType type,
+                                         const InitCallback& callback);
 
   // ModelTypeStore implementation.
   void ReadData(const IdList& id_list,
@@ -71,10 +72,6 @@ class ModelTypeStoreImpl : public ModelTypeStore, public base::NonThreadSafe {
       const InitCallback& callback,
       scoped_refptr<ModelTypeStoreBackend> backend);
 
-  // Format prefix key for data/metadata records with |type|.
-  static std::string FormatDataPrefix(const ModelType type);
-  static std::string FormatMetaPrefix(const ModelType type);
-
   static leveldb::WriteBatch* GetLeveldbWriteBatch(WriteBatch* write_batch);
 
   // Format key for data/metadata records with given id.
@@ -115,6 +112,9 @@ class ModelTypeStoreImpl : public ModelTypeStore, public base::NonThreadSafe {
   const std::string data_prefix_;
   const std::string metadata_prefix_;
 
+  // Key for this type's global metadata record.
+  const std::string global_metadata_key_;
+
   base::WeakPtrFactory<ModelTypeStoreImpl> weak_ptr_factory_;
 };