Use a two-part data format version in IndexedDB metadata.

content/browser/indexed_db/indexed_db_factory_impl.h

Index: content/browser/indexed_db/indexed_db_factory_impl.h
diff --git a/content/browser/indexed_db/indexed_db_factory_impl.h b/content/browser/indexed_db/indexed_db_factory_impl.h
index 12617f8ce2fc318e8e14175a406c4cc111e7cb87..410ed4367516cc222ccecc0e08e03e77abd8217e 100644
--- a/content/browser/indexed_db/indexed_db_factory_impl.h
+++ b/content/browser/indexed_db/indexed_db_factory_impl.h
@@ -32,16 +32,20 @@ class CONTENT_EXPORT IndexedDBFactoryImpl : public IndexedDBFactory {
   void ReleaseDatabase(const IndexedDBDatabase::Identifier& identifier,
                        bool forced_close) override;
 
-  void GetDatabaseNames(scoped_refptr<IndexedDBCallbacks> callbacks,
-                        const url::Origin& origin,
-                        const base::FilePath& data_directory,
-                        scoped_refptr<net::URLRequestContextGetter>
-                            request_context_getter) override;
-  void Open(const base::string16& name,
-            std::unique_ptr<IndexedDBPendingConnection> connection,
-            scoped_refptr<net::URLRequestContextGetter> request_context_getter,
-            const url::Origin& origin,
-            const base::FilePath& data_directory) override;
+  void GetDatabaseNames(
+      scoped_refptr<IndexedDBCallbacks> callbacks,
+      const url::Origin& origin,
+      const base::FilePath& data_directory,
+      const IndexedDBDataFormatVersion& client_data_format_version,
+      scoped_refptr<net::URLRequestContextGetter> request_context_getter)
+      override;
+  void Open(
+      const base::string16& name,
+      std::unique_ptr<IndexedDBPendingConnection> connection,
+      scoped_refptr<net::URLRequestContextGetter> request_context_getter,
+      const url::Origin& origin,
+      const base::FilePath& data_directory,
+      const IndexedDBDataFormatVersion& client_data_format_version) override;
 
   void DeleteDatabase(
       const base::string16& name,
@@ -49,6 +53,7 @@ class CONTENT_EXPORT IndexedDBFactoryImpl : public IndexedDBFactory {
       scoped_refptr<IndexedDBCallbacks> callbacks,
       const url::Origin& origin,
       const base::FilePath& data_directory,
+      const IndexedDBDataFormatVersion& client_data_format_version,
       bool force_close) override;
 
   void HandleBackingStoreFailure(const url::Origin& origin) override;
@@ -79,6 +84,7 @@ class CONTENT_EXPORT IndexedDBFactoryImpl : public IndexedDBFactory {
   scoped_refptr<IndexedDBBackingStore> OpenBackingStore(
       const url::Origin& origin,
       const base::FilePath& data_directory,
+      const IndexedDBDataFormatVersion& client_data_format_version,
       scoped_refptr<net::URLRequestContextGetter> request_context_getter,
       IndexedDBDataLossInfo* data_loss_info,
       bool* disk_full,
@@ -87,6 +93,7 @@ class CONTENT_EXPORT IndexedDBFactoryImpl : public IndexedDBFactory {
   scoped_refptr<IndexedDBBackingStore> OpenBackingStoreHelper(
       const url::Origin& origin,
       const base::FilePath& data_directory,
+      const IndexedDBDataFormatVersion& client_data_format_version,
       scoped_refptr<net::URLRequestContextGetter> request_context_getter,
       IndexedDBDataLossInfo* data_loss_info,
       bool* disk_full,