DOMException toString is not correct

LayoutTests/fast/speech/scripted/start-exception.html

Index: LayoutTests/fast/speech/scripted/start-exception.html
diff --git a/LayoutTests/fast/speech/scripted/start-exception.html b/LayoutTests/fast/speech/scripted/start-exception.html
index 890fd4e8345ca95287a6663f839645b63378fc40..d16ca4a77975b1f86502683a25848dca2ac04655 100644
--- a/LayoutTests/fast/speech/scripted/start-exception.html
+++ b/LayoutTests/fast/speech/scripted/start-exception.html
@@ -34,14 +34,14 @@ function doubleStart() {
                         finishJSTest();
                     }
                 } else {
-                    shouldThrow("r.start()", '"Error: InvalidStateError: DOM Exception 11"');
+                    shouldThrow("r.start()", '"InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable."');
                 }
             }
         }
     }
 
     shouldNotThrow("r.start()");
-    shouldThrow("r.start()", '"Error: InvalidStateError: DOM Exception 11"');
+    shouldThrow("r.start()", '"InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable."');
 }
 
 window.onload = run;