Remove more oilpan.

sky/engine/core/dom/custom/CustomElementMicrotaskStep.h

 /*
  * Copyright (C) 2013 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 18 matching lines @@
  */
 
 #ifndef CustomElementMicrotaskStep_h
 #define CustomElementMicrotaskStep_h
 
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
-class CustomElementMicrotaskStep : public DummyBase<CustomElementMicrotaskStep> {
+class CustomElementMicrotaskStep {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskStep);
 public:
     CustomElementMicrotaskStep() { }
     virtual ~CustomElementMicrotaskStep() { }
 
     enum Result {
         Processing,
         FinishedProcessing
     };
 
     virtual Result process() = 0;
 
     virtual void trace(Visitor*) { }
 };
 
 }
 
 #endif // CustomElementMicrotaskStep_h