Oilpan: fix build after r200992.

Source/core/dom/ScriptedIdleTaskController.h

Index: Source/core/dom/ScriptedIdleTaskController.h
diff --git a/Source/core/dom/ScriptedIdleTaskController.h b/Source/core/dom/ScriptedIdleTaskController.h
index f6805a19d8f5acf9c9772d4d200efbc4ff27683a..295cbcac391e6b5077ef04b2ecbff7e1d957b830 100644
--- a/Source/core/dom/ScriptedIdleTaskController.h
+++ b/Source/core/dom/ScriptedIdleTaskController.h
@@ -19,13 +19,15 @@ class ExecutionContext;
 class IdleRequestCallback;
 class DocumentLoadTiming;
 
-class ScriptedIdleTaskController : public RefCountedWillBeGarbageCollected<ScriptedIdleTaskController>, public ActiveDOMObject {
-    DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(ScriptedIdleTaskController);
+class ScriptedIdleTaskController : public RefCountedWillBeGarbageCollectedFinalized<ScriptedIdleTaskController>, public ActiveDOMObject {
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ScriptedIdleTaskController);
 public:
     static PassRefPtrWillBeRawPtr<ScriptedIdleTaskController> create(ExecutionContext* context, const DocumentLoadTiming& timing)
     {
         return adoptRefWillBeNoop(new ScriptedIdleTaskController(context, timing));
     }
+    ~ScriptedIdleTaskController();
+
     DECLARE_TRACE();
 
     using CallbackId = int;