Oilpan: fix build after r187279.

Source/core/storage/DOMWindowStorageController.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/storage/DOMWindowStorageController.h"
 
 #include "core/dom/Document.h"
 #include "core/events/Event.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/page/Page.h"
 
 namespace blink {
 
 DOMWindowStorageController::DOMWindowStorageController(Document& document)
     : DOMWindowLifecycleObserver(document.domWindow())
     , m_document(document)
 {
 }
 
 DOMWindowStorageController::~DOMWindowStorageController()
 {
 }
 
+void DOMWindowStorageController::trace(Visitor* visitor)
+{
+    visitor->trace(m_document);
+    WillBeHeapSupplement<Document>::trace(visitor);
+}
+
 // static
 const char* DOMWindowStorageController::supplementName()
 {
     return "DOMWindowStorageController";
 }
 
 // static
 DOMWindowStorageController& DOMWindowStorageController::from(Document& document)
 {
     DOMWindowStorageController* controller = static_cast<DOMWindowStorageController*>(WillBeHeapSupplement<Document>::from(document, supplementName()));
@@ skipping 10 matching lines @@
         // Creating these blink::Storage objects informs the system that we'd like to receive
         // notifications about storage events that might be triggered in other processes. Rather
         // than subscribe to these notifications explicitly, we subscribe to them implicitly to
         // simplify the work done by the system.
         window->localStorage(IGNORE_EXCEPTION);
         window->sessionStorage(IGNORE_EXCEPTION);
     }
 }
 
 } // namespace blink