IDL: make optional arguments (without default) explicit sometimes

Source/core/css/FontFaceSet.cpp

Index: Source/core/css/FontFaceSet.cpp
diff --git a/Source/core/css/FontFaceSet.cpp b/Source/core/css/FontFaceSet.cpp
index 253e7db3f7e2b167c1469b4e2edbe8f8b149115d..23f6ca77e7f938eb4842997f9131749ce355140f 100644
--- a/Source/core/css/FontFaceSet.cpp
+++ b/Source/core/css/FontFaceSet.cpp
@@ -357,17 +357,7 @@ bool FontFaceSet::isCSSConnectedFontFace(FontFace* fontFace) const
     return cssConnectedFontFaceList().contains(fontFace);
 }
 
-void FontFaceSet::forEach(PassOwnPtr<FontFaceSetForEachCallback> callback, ScriptValue& thisArg) const
-{
-    forEachInternal(callback, &thisArg);
-}
-
-void FontFaceSet::forEach(PassOwnPtr<FontFaceSetForEachCallback> callback) const
-{
-    forEachInternal(callback, 0);
-}
-
-void FontFaceSet::forEachInternal(PassOwnPtr<FontFaceSetForEachCallback> callback, ScriptValue* thisArg) const
+void FontFaceSet::forEach(PassOwnPtr<FontFaceSetForEachCallback> callback, const Optional<ScriptValue>& thisArg) const
 {
     if (!inActiveDocumentContext())
         return;
@@ -381,10 +371,10 @@ void FontFaceSet::forEachInternal(PassOwnPtr<FontFaceSetForEachCallback> callbac
 
     for (size_t i = 0; i < fontFaces.size(); ++i) {
         FontFace* face = fontFaces[i].get();
-        if (thisArg)
-            callback->handleItem(*thisArg, face, face, const_cast<FontFaceSet*>(this));
-        else
+        if (thisArg.isMissing())
             callback->handleItem(face, face, const_cast<FontFaceSet*>(this));
+        else
+            callback->handleItem(thisArg.get(), face, face, const_cast<FontFaceSet*>(this));
     }
 }