Oilpan: fix build after r192098.

Source/core/inspector/InspectorOverlay.h

Index: Source/core/inspector/InspectorOverlay.h
diff --git a/Source/core/inspector/InspectorOverlay.h b/Source/core/inspector/InspectorOverlay.h
index 918ba8e3f86aa7a4823d540ba8ecb356ae335d35..d89407d501b2b1ca7f3c1c5e1bda54aef2d2e719 100644
--- a/Source/core/inspector/InspectorOverlay.h
+++ b/Source/core/inspector/InspectorOverlay.h
@@ -38,7 +38,7 @@ namespace blink {
 
 struct InspectorHighlightConfig;
 
-class InspectorOverlay : public NoBaseWillBeGarbageCollectedFinalized<InspectorOverlay> {
+class InspectorOverlay : public WillBeGarbageCollectedMixin {
 public:
     virtual ~InspectorOverlay() { }
 
@@ -52,6 +52,8 @@ public:
     virtual void suspendUpdates() = 0;
     virtual void resumeUpdates() = 0;
 
+    DEFINE_INLINE_VIRTUAL_TRACE() { }
+
     class Listener : public WillBeGarbageCollectedMixin {
     public:
         virtual ~Listener() { }