Inherit EventTarget interface instead of duplicating its code

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 885810db4a493f01736abc427e9eb8fda190da5f..993f829f674ea4fdbc5d264d66b83facfa343a28 100644
--- a/Source/modules/indexeddb/IDBTransaction.h
+++ b/Source/modules/indexeddb/IDBTransaction.h
@@ -48,7 +48,7 @@ class IDBObjectStore;
 class IDBOpenDBRequest;
 struct IDBObjectStoreMetadata;
 
-class IDBTransaction : public ScriptWrappable, public RefCounted<IDBTransaction>, public EventTarget, public ActiveDOMObject {
+class IDBTransaction : public EventTarget, public ScriptWrappable, public RefCounted<IDBTransaction>, public ActiveDOMObject {
 public:
     static PassRefPtr<IDBTransaction> create(ScriptExecutionContext*, int64_t, const Vector<String>& objectStoreNames, IndexedDB::TransactionMode, IDBDatabase*);
     static PassRefPtr<IDBTransaction> create(ScriptExecutionContext*, int64_t, IDBDatabase*, IDBOpenDBRequest*, const IDBDatabaseMetadata& previousMetadata);