Oilpan: fix build after r201436, r201444.

Source/core/inspector/LayoutEditor.h

Index: Source/core/inspector/LayoutEditor.h
diff --git a/Source/core/inspector/LayoutEditor.h b/Source/core/inspector/LayoutEditor.h
index 29c25cf7c4c1f8852a00a600a9a528f7469406ff..f23d850ed13472d4598941341a59acecc28f73cd 100644
--- a/Source/core/inspector/LayoutEditor.h
+++ b/Source/core/inspector/LayoutEditor.h
@@ -21,8 +21,7 @@ class InspectorCSSAgent;
 class JSONArray;
 class JSONObject;
 
-class CORE_EXPORT LayoutEditor final: public NoBaseWillBeGarbageCollectedFinalized<LayoutEditor> {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(LayoutEditor);
+class CORE_EXPORT LayoutEditor final : public NoBaseWillBeGarbageCollectedFinalized<LayoutEditor> {
 public:
     static PassOwnPtrWillBeRawPtr<LayoutEditor> create(InspectorCSSAgent* cssAgent)
     {
@@ -35,7 +34,7 @@ public:
     void overlayPropertyChanged(float);
     void overlayEndedPropertyChange();
 
-    DECLARE_VIRTUAL_TRACE();
+    DECLARE_TRACE();
 
 private:
     explicit LayoutEditor(InspectorCSSAgent*);