Oilpan: Build fix after r170389

Source/core/events/ApplicationCacheErrorEvent.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/events/ApplicationCacheErrorEvent.h"
 
 namespace WebCore {
 
 static const String& errorReasonToString(blink::WebApplicationCacheHost::ErrorReason reason)
@@ skipping 56 matching lines @@
     , m_status(initializer.status)
     , m_message(initializer.message)
 {
     ScriptWrappable::init(this);
 }
 
 ApplicationCacheErrorEvent::~ApplicationCacheErrorEvent()
 {
 }
 
+void ApplicationCacheErrorEvent::trace(Visitor* visitor)
+{
+    Event::trace(visitor);
+}
+
 } // namespace WebCore