Add missing traces for Supplement<> classes

third_party/WebKit/Source/core/dom/DocumentParserTiming.cpp

 // Copyright 2015 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 "core/dom/DocumentParserTiming.h"
 
 #include "core/dom/Document.h"
 #include "core/loader/DocumentLoader.h"
 #include "platform/TraceEvent.h"
 
@@ skipping 41 matching lines @@
         return;
     m_parserBlockedOnScriptLoadDuration += duration;
     if (scriptInsertedViaDocumentWrite)
         m_parserBlockedOnScriptLoadFromDocumentWriteDuration += duration;
     notifyDocumentParserTimingChanged();
 }
 
 DEFINE_TRACE(DocumentParserTiming)
 {
     visitor->trace(m_document);
+    Supplement<Document>::trace(visitor);
 }
 
 DocumentParserTiming::DocumentParserTiming(Document& document)
     : m_document(document)
 {
 }
 
 void DocumentParserTiming::notifyDocumentParserTimingChanged()
 {
     if (m_document->loader())
         m_document->loader()->didChangePerformanceTiming();
 }
 
 } // namespace blink