Oilpan: Fix compile after r200678.

Source/core/inspector/WorkerDebuggerAgent.h

 /*
  * Copyright (C) 2011 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 23 matching lines @@
 #include "core/inspector/InspectorDebuggerAgent.h"
 
 namespace blink {
 
 class WorkerGlobalScope;
 class WorkerThreadDebugger;
 
 class WorkerDebuggerAgent final : public InspectorDebuggerAgent {
     WTF_MAKE_NONCOPYABLE(WorkerDebuggerAgent);
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(WorkerDebuggerAgent);
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(WorkerDebuggerAgent);
 public:
     static PassOwnPtrWillBeRawPtr<WorkerDebuggerAgent> create(WorkerThreadDebugger*, WorkerGlobalScope*, InjectedScriptManager*);
     ~WorkerDebuggerAgent() override;
     DECLARE_VIRTUAL_TRACE();
 
 private:
     WorkerDebuggerAgent(WorkerThreadDebugger*, WorkerGlobalScope*, InjectedScriptManager*);
 
     // V8DebuggerAgent::Client implemntation.
     InjectedScript defaultInjectedScript() override;
     void muteConsole() override;
     void unmuteConsole() override;
 
     RawPtrWillBeMember<WorkerGlobalScope> m_inspectedWorkerGlobalScope;
 };
 
 } // namespace blink
 
 #endif // !defined(WorkerDebuggerAgent_h)