Change IllegalArgumentException to ArgumentError.

utils/pub/package.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.
 
 #library('package');
 
 #import('io.dart');
 #import('pubspec.dart');
 #import('source.dart');
 #import('source_registry.dart');
@@ skipping 117 matching lines @@
     // enough to uniquely identify the package and that we don't need to delve
     // into the description.
     return other.name == name &&
            other.source.name == source.name &&
            other.version == version;
   }
 
   String toString() => "$name $version from ${source.name}";
 
   int compareTo(Comparable other) {
-    if (other is! PackageId) throw new IllegalArgumentException(other);
+    if (other is! PackageId) throw new ArgumentError(other);
 
     var sourceComp = source.name.compareTo(other.source.name);
     if (sourceComp != 0) return sourceComp;
 
     var nameComp = name.compareTo(other.name);
     if (nameComp != 0) return nameComp;
 
     return version.compareTo(other.version);
   }
 
@@ skipping 64 matching lines @@
 
 class PubspecNameMismatchException implements Exception {
   final String expectedName;
   final String actualName;
 
   PubspecNameMismatchException(this.expectedName, this.actualName);
 
   String toString() => 'The name you specified for your dependency, '
     '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
 }