Sync the DOMImplementation interface with the spec

Source/core/dom/DOMImplementation.h

Index: Source/core/dom/DOMImplementation.h
diff --git a/Source/core/dom/DOMImplementation.h b/Source/core/dom/DOMImplementation.h
index a5fe6108e1f47ffb319ebae9300bc869480e325e..152acba2755bd66d5db00b45eb630e23434f97a7 100644
--- a/Source/core/dom/DOMImplementation.h
+++ b/Source/core/dom/DOMImplementation.h
@@ -60,7 +60,7 @@ public:
     PassRefPtrWillBeRawPtr<XMLDocument> createDocument(const AtomicString& namespaceURI, const AtomicString& qualifiedName, DocumentType*, ExceptionState&);
 
     // From the HTMLDOMImplementation interface
-    PassRefPtrWillBeRawPtr<HTMLDocument> createHTMLDocument(const String& title);
+    PassRefPtrWillBeRawPtr<HTMLDocument> createHTMLDocument(const String& title = String());
 
     // Other methods (not part of DOM)
     static PassRefPtrWillBeRawPtr<Document> createDocument(const String& mimeType, const DocumentInit&, bool inViewSourceMode);