IDL: make optional arguments (without default) explicit sometimes

Source/modules/serviceworkers/Headers.cpp

Index: Source/modules/serviceworkers/Headers.cpp
diff --git a/Source/modules/serviceworkers/Headers.cpp b/Source/modules/serviceworkers/Headers.cpp
index 0493a4cd859f4b12aae4263e09e138d5d5cfd2ba..e4e1933ab864a2d4b1842165ff28bcb321242e2b 100644
--- a/Source/modules/serviceworkers/Headers.cpp
+++ b/Source/modules/serviceworkers/Headers.cpp
@@ -210,14 +210,17 @@ void Headers::set(const String& name, const String& value, ExceptionState& excep
     m_headerList->set(name, value);
 }
 
-void Headers::forEach(PassOwnPtr<HeadersForEachCallback> callback, ScriptValue& thisArg)
+void Headers::forEach(PassOwnPtr<HeadersForEachCallback> callback, const Optional<ScriptValue>& thisArg)
 {
-    forEachInternal(callback, &thisArg);
-}
-
-void Headers::forEach(PassOwnPtr<HeadersForEachCallback> callback)
-{
-    forEachInternal(callback, 0);
+    TrackExceptionState exceptionState;
+    for (size_t i = 0; i < m_headerList->size(); ++i) {
+        if (thisArg.isMissing())
+            callback->handleItem(m_headerList->list()[i]->second, m_headerList->list()[i]->first, this);
+        else
+            callback->handleItem(thisArg.get(), m_headerList->list()[i]->second, m_headerList->list()[i]->first, this);
+        if (exceptionState.hadException())
+            break;
+    }
 }
 
 void Headers::fillWith(const Headers* object, ExceptionState& exceptionState)
@@ -309,19 +312,6 @@ Headers::Headers(FetchHeaderList* headerList)
     ScriptWrappable::init(this);
 }
 
-void Headers::forEachInternal(PassOwnPtr<HeadersForEachCallback> callback, ScriptValue* thisArg)
-{
-    TrackExceptionState exceptionState;
-    for (size_t i = 0; i < m_headerList->size(); ++i) {
-        if (thisArg)
-            callback->handleItem(*thisArg, m_headerList->list()[i]->second, m_headerList->list()[i]->first, this);
-        else
-            callback->handleItem(m_headerList->list()[i]->second, m_headerList->list()[i]->first, this);
-        if (exceptionState.hadException())
-            break;
-    }
-}
-
 void Headers::trace(Visitor* visitor)
 {
     visitor->trace(m_headerList);