Fix name of the toString method on error objects. Bug caught by layout tests.

TBR=sgjesse@chromium.org
Review URL: http://codereview.chromium.org/6258004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6328 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/messages.js

@@ -1014,6 +1014,8 @@ function errorToString() {
   var message = this.hasOwnProperty("message") ? (": " + this.message) : "";
   return this.name + message;
 }
+
+%FunctionSetName(errorToString, 'toString');
 %SetProperty($Error.prototype, 'toString', errorToString, DONT_ENUM);