Rework dispatchEvent so it is consistent for isTrusted support.

Source/modules/indexeddb/IDBTransaction.h

Index: Source/modules/indexeddb/IDBTransaction.h
diff --git a/Source/modules/indexeddb/IDBTransaction.h b/Source/modules/indexeddb/IDBTransaction.h
index b5e7251675dd7c4e1f2edb185635e606f1de3b70..c269707227ee6a37b57c8941e1c71d2be08755b0 100644
--- a/Source/modules/indexeddb/IDBTransaction.h
+++ b/Source/modules/indexeddb/IDBTransaction.h
@@ -99,13 +99,14 @@ public:
     const AtomicString& interfaceName() const override;
     ExecutionContext* executionContext() const override;
 
-    using EventTarget::dispatchEvent;
-    bool dispatchEvent(PassRefPtrWillBeRawPtr<Event>) override;
-
     // ActiveDOMObject
     bool hasPendingActivity() const override;
     void stop() override;
 
+protected:
+    // EventTarget
+    bool dispatchEventInternal(PassRefPtrWillBeRawPtr<Event>) override;
+
 private:
     IDBTransaction(ScriptState*, int64_t, const HashSet<String>&, WebIDBTransactionMode, IDBDatabase*, IDBOpenDBRequest*, const IDBDatabaseMetadata&);