Add the backchannel for Blobs to be received into Blink from the database backend.

public/platform/WebIDBDatabase.h

Index: public/platform/WebIDBDatabase.h
diff --git a/public/platform/WebIDBDatabase.h b/public/platform/WebIDBDatabase.h
index 379ff8770a35151cba4788eaa7ab18a122659b9b..9ecc7b036cea70c5697282654a270452b2501ffd 100644
--- a/public/platform/WebIDBDatabase.h
+++ b/public/platform/WebIDBDatabase.h
@@ -89,6 +89,7 @@ public:
     virtual void count(long long transactionId, long long objectStoreId, long long indexId, const WebIDBKeyRange&, WebIDBCallbacks*) { BLINK_ASSERT_NOT_REACHED(); }
     virtual void deleteRange(long long transactionId, long long objectStoreId, const WebIDBKeyRange&, WebIDBCallbacks*) { BLINK_ASSERT_NOT_REACHED(); }
     virtual void clear(long long transactionId, long long objectStoreId, WebIDBCallbacks*) { BLINK_ASSERT_NOT_REACHED(); }
+    virtual void ackReceivedBlobs(const WebVector<WebString>& uuids) { BLINK_ASSERT_NOT_REACHED(); }
 
 protected:
     WebIDBDatabase() { }