Oilpan: trace non-owned InspectorOverlay references.

Source/core/inspector/InspectorDOMAgent.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 242 matching lines @@
     void discardFrontendBindings();
 
     void innerHighlightQuad(PassOwnPtr<FloatQuad>, const RefPtr<JSONObject>* color, const RefPtr<JSONObject>* outlineColor);
 
     bool pushDocumentUponHandlelessOperation(ErrorString*);
 
     RawPtrWillBeMember<InspectorRevalidateDOMTask> revalidateTask();
 
     RawPtrWillBeMember<InspectorPageAgent> m_pageAgent;
     RawPtrWillBeMember<InjectedScriptManager> m_injectedScriptManager;
-    InspectorOverlay* m_overlay;
+    RawPtrWillBeMember<InspectorOverlay> m_overlay;
     InspectorFrontend::DOM* m_frontend;
     RawPtrWillBeMember<DOMListener> m_domListener;
     OwnPtrWillBeMember<NodeToIdMap> m_documentNodeToIdMap;
     // Owns node mappings for dangling nodes.
     WillBeHeapVector<OwnPtrWillBeMember<NodeToIdMap> > m_danglingNodeToIdMaps;
     WillBeHeapHashMap<int, RawPtrWillBeMember<Node> > m_idToNode;
     WillBeHeapHashMap<int, RawPtrWillBeMember<NodeToIdMap> > m_idToNodesMap;
     HashSet<int> m_childrenRequested;
     HashSet<int> m_distributedNodesRequested;
     HashMap<int, int> m_cachedChildCount;
     int m_lastNodeId;
     RefPtrWillBeMember<Document> m_document;
     typedef WillBeHeapHashMap<String, WillBeHeapVector<RefPtrWillBeMember<Node> > > SearchResults;
     SearchResults m_searchResults;
     OwnPtrWillBeMember<InspectorRevalidateDOMTask> m_revalidateTask;
     SearchMode m_searchingForNode;
     OwnPtr<HighlightConfig> m_inspectModeHighlightConfig;
     OwnPtrWillBeMember<InspectorHistory> m_history;
     OwnPtrWillBeMember<DOMEditor> m_domEditor;
     bool m_suppressAttributeModifiedEvent;
     RawPtrWillBeMember<Listener> m_listener;
     int m_backendNodeIdToInspect;
 };
 
 
 } // namespace blink
 
 #endif // !defined(InspectorDOMAgent_h)