Make some ScriptValue references const

Source/core/css/FontFaceSet.h

Index: Source/core/css/FontFaceSet.h
diff --git a/Source/core/css/FontFaceSet.h b/Source/core/css/FontFaceSet.h
index 19a01bcc8eaf316131e723188d98bbc7d06c0fa9..c6202ae12a1994b62bc34e9d93ae0324a275adce 100644
--- a/Source/core/css/FontFaceSet.h
+++ b/Source/core/css/FontFaceSet.h
@@ -80,7 +80,7 @@ public:
     void add(FontFace*, ExceptionState&);
     void clear();
     bool remove(FontFace*, ExceptionState&);
-    void forEach(PassOwnPtr<FontFaceSetForEachCallback>, ScriptValue& thisArg) const;
+    void forEach(PassOwnPtr<FontFaceSetForEachCallback>, const ScriptValue& thisArg) const;
     void forEach(PassOwnPtr<FontFaceSetForEachCallback>) const;
     bool has(FontFace*, ExceptionState&) const;
 
@@ -136,7 +136,7 @@ private:
     bool hasLoadedFonts() const { return !m_loadedFonts.isEmpty() || !m_failedFonts.isEmpty(); }
 
     bool inActiveDocumentContext() const;
-    void forEachInternal(PassOwnPtr<FontFaceSetForEachCallback>, ScriptValue* thisArg) const;
+    void forEachInternal(PassOwnPtr<FontFaceSetForEachCallback>, const ScriptValue* thisArg) const;
     void addToLoadingFonts(PassRefPtrWillBeRawPtr<FontFace>);
     void removeFromLoadingFonts(PassRefPtrWillBeRawPtr<FontFace>);
     void fireLoadingEvent();