Oilpan: fix build after r187362.

Source/core/inspector/InspectorDebuggerAgent.h

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010-2011 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 50 matching lines @@
 class ScriptSourceCode;
 
 typedef String ErrorString;
 
 class InspectorDebuggerAgent
     : public InspectorBaseAgent<InspectorDebuggerAgent>
     , public ScriptDebugListener
     , public InspectorBackendDispatcher::DebuggerCommandHandler {
     WTF_MAKE_NONCOPYABLE(InspectorDebuggerAgent);
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(InspectorDebuggerAgent);
 public:
     enum BreakpointSource {
         UserBreakpointSource,
         DebugCommandBreakpointSource,
         MonitorCommandBreakpointSource
     };
 
     static const char backtraceObjectGroup[];
 
     ~InspectorDebuggerAgent() override;
@@ skipping 202 matching lines @@
     unsigned m_maxAsyncCallStackDepth;
     RefPtrWillBeMember<AsyncCallChain> m_currentAsyncCallChain;
     unsigned m_nestedAsyncCallCount;
     bool m_performingAsyncStepIn;
 };
 
 } // namespace blink
 
 
 #endif // !defined(InspectorDebuggerAgent_h)