Change IllegalArgumentException to ArgumentError.

runtime/bin/process.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /** Exit the Dart VM process with the given [status] code. */
 void exit(int status) {
   if (status is !int) {
-    throw new IllegalArgumentException("int status expected");
+    throw new ArgumentError("int status expected");
   }
   _exit(status);
 }
 
 /**
  * [Process] is used to start new processes using the static
  * [start] and [run] methods.
  */
 class Process {
   /**
@@ skipping 216 matching lines @@
   /**
    * Contains the system message for the process exception if any.
    */
   final String message;
 
   /**
    * Contains the OS error code for the process exception if any.
    */
   final int errorCode;
 }