Enable Oilpan by default in modules/filesystem/

Source/modules/filesystem/FileWriterBase.h

Index: Source/modules/filesystem/FileWriterBase.h
diff --git a/Source/modules/filesystem/FileWriterBase.h b/Source/modules/filesystem/FileWriterBase.h
index a9d59dc7649af16baa1b9e0b2ec2dd7731538161..39bcf0bc1df7986508e24fff3fdf15723b32655d 100644
--- a/Source/modules/filesystem/FileWriterBase.h
+++ b/Source/modules/filesystem/FileWriterBase.h
@@ -34,13 +34,12 @@
 #include "platform/heap/Handle.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
-#include "wtf/RefCounted.h"
 
 namespace blink { class WebFileWriter; }
 
 namespace WebCore {
 
-class FileWriterBase : public RefCountedWillBeRefCountedGarbageCollected<FileWriterBase> {
+class FileWriterBase : public RefCountedGarbageCollected<FileWriterBase> {
 public:
     virtual ~FileWriterBase();
     void initialize(PassOwnPtr<blink::WebFileWriter>, long long length);