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

content/browser/indexed_db/indexed_db_dispatcher_host.h

Index: content/browser/indexed_db/indexed_db_dispatcher_host.h
diff --git a/content/browser/indexed_db/indexed_db_dispatcher_host.h b/content/browser/indexed_db/indexed_db_dispatcher_host.h
index e24caf71e26f8294c4ca2ba6b4cf471dd6d7c83d..4d0541e2465bc4c0a0f04df9e2801a896ec60bec 100644
--- a/content/browser/indexed_db/indexed_db_dispatcher_host.h
+++ b/content/browser/indexed_db/indexed_db_dispatcher_host.h
@@ -15,6 +15,7 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/optional.h"
 #include "content/browser/blob_storage/chrome_blob_storage_context.h"
 #include "content/common/indexed_db/indexed_db.mojom.h"
 #include "content/public/browser/browser_thread.h"
@@ -64,6 +65,8 @@ class IndexedDBDispatcherHost
   ~IndexedDBDispatcherHost() override;
 
   // indexed_db::mojom::Factory implementation:
+  void Configure(
+      const IndexedDBDataFormatVersion& client_data_format_version) override;
   void GetDatabaseNames(
       ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info,
       const url::Origin& origin) override;
@@ -80,6 +83,8 @@ class IndexedDBDispatcherHost
       const base::string16& name,
       bool force_close) override;
 
+  void ConfigureOnIDBThread(
+      const IndexedDBDataFormatVersion& client_data_format_version);
   void GetDatabaseNamesOnIDBThread(scoped_refptr<IndexedDBCallbacks> callbacks,
                                    const url::Origin& origin);
   void OpenOnIDBThread(
@@ -110,6 +115,10 @@ class IndexedDBDispatcherHost
   // Used to set file permissions for blob storage.
   const int ipc_process_id_;
 
+  // The reported data format version supported by the client, used when opening
+  // the backing store. Only accessed on the IDB thread.
+  base::Optional<IndexedDBDataFormatVersion> client_data_format_version_;
+
   mojo::AssociatedBindingSet<::indexed_db::mojom::Factory> bindings_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IndexedDBDispatcherHost);