Simplify Supplementables post Oilpan.

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

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2012 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 258 matching lines @@
     return nullptr;
 }
 
 void ExecutionContext::removeURLFromMemoryCache(const KURL& url)
 {
     memoryCache()->removeURLFromCache(url);
 }
 
 DEFINE_TRACE(ExecutionContext)
 {
-#if ENABLE(OILPAN)
     visitor->trace(m_publicURLManager);
-    HeapSupplementable<ExecutionContext>::trace(visitor);
-#endif
     ContextLifecycleNotifier::trace(visitor);
+    Supplementable<ExecutionContext>::trace(visitor);
 }
 
 } // namespace blink