rAc: make requestAutocomplete() return a promise.

Source/core/dom/DOMException.h

Index: Source/core/dom/DOMException.h
diff --git a/Source/core/dom/DOMException.h b/Source/core/dom/DOMException.h
index ade90d63abfc3dfeb2266939ed9c46ff029c9c94..13c33ef53e1ab9ffcd29d114d02e27b63699b5fb 100644
--- a/Source/core/dom/DOMException.h
+++ b/Source/core/dom/DOMException.h
@@ -56,9 +56,10 @@ public:
     static String getErrorName(ExceptionCode);
     static String getErrorMessage(ExceptionCode);
 
-private:
-    DOMException(unsigned short m_code, const String& name, const String& sanitizedMessage, const String& unsanitizedMessage);
+protected:
+    DOMException(unsigned short m_code, const String& name, const String& sanitizedMessage = String(), const String& unsanitizedMessage = String());
 
+private:
     unsigned short m_code;
     String m_name;
     String m_sanitizedMessage;