remove use of {,un}setPendingActivity from DOMFileSystem.

Source/modules/filesystem/DOMFileSystem.h

Index: Source/modules/filesystem/DOMFileSystem.h
diff --git a/Source/modules/filesystem/DOMFileSystem.h b/Source/modules/filesystem/DOMFileSystem.h
index 623feac7244de26a81404bb17a658fc2b610d549..45d2ad6925e0687c87fcedad4d40ba30936b9c0d 100644
--- a/Source/modules/filesystem/DOMFileSystem.h
+++ b/Source/modules/filesystem/DOMFileSystem.h
@@ -61,6 +61,9 @@ public:
     virtual void removePendingCallbacks() OVERRIDE;
     virtual void reportError(PassOwnPtr<ErrorCallback>, PassRefPtrWillBeRawPtr<FileError>) OVERRIDE;
 
+    // ActiveDOMObject overrides.
+    virtual bool hasPendingActivity() const OVERRIDE;
+
     void createWriter(const FileEntry*, PassOwnPtr<FileWriterCallback>, PassOwnPtr<ErrorCallback>);
     void createFile(const FileEntry*, PassOwnPtr<FileCallback>, PassOwnPtr<ErrorCallback>);
 
@@ -125,6 +128,8 @@ private:
         OwnPtr<CB> m_callback;
         CBArg m_callbackArg;
     };
+
+    int m_numberOfPendingCallbacks;
 };
 
 template <typename CB, typename CBArg>