Replace uses of {un}setPendingActivity() in FetchBodyStream.

Source/modules/serviceworkers/FetchBodyStream.h

Index: Source/modules/serviceworkers/FetchBodyStream.h
diff --git a/Source/modules/serviceworkers/FetchBodyStream.h b/Source/modules/serviceworkers/FetchBodyStream.h
index 08773466aafa60c86756c4f7071b81096214ad7a..6ea413672ab70583ad682dabd4f8c94b55704dea 100644
--- a/Source/modules/serviceworkers/FetchBodyStream.h
+++ b/Source/modules/serviceworkers/FetchBodyStream.h
@@ -20,11 +20,8 @@ namespace WebCore {
 
 class ScriptState;
 
-// FIXME: Oilpan: when the implementation stops using
-// ActiveDOMObject::(un)setPendingActivity, derive from
-// RefCountedWillBeGarbageCollectedFinalized instead.
 class FetchBodyStream FINAL
-    : public RefCountedWillBeRefCountedGarbageCollected<FetchBodyStream>
+    : public RefCountedWillBeGarbageCollectedFinalized<FetchBodyStream>
     , public ScriptWrappable
     , public ActiveDOMObject
     , public FileReaderLoaderClient {
@@ -48,6 +45,7 @@ public:
 
     // ActiveDOMObject override.
     virtual void stop() OVERRIDE;
+    virtual bool hasPendingActivity() const OVERRIDE;
 
     void trace(Visitor*) { }