Change new List(n) to return fixed length list.

pkg/args/lib/args.dart

Index: pkg/args/lib/args.dart
diff --git a/pkg/args/lib/args.dart b/pkg/args/lib/args.dart
index 29da1e262b840885b6d87c41474eec6aa6f0d418..7760a99f53edff164670dba4b5b3ad96dd0d4511 100644
--- a/pkg/args/lib/args.dart
+++ b/pkg/args/lib/args.dart
@@ -307,7 +307,7 @@ class ArgParser {
    * flags and options defined by this parser, and returns the result.
    */
   ArgResults parse(List<String> args) =>
-      new Parser(null, this, args.toList()).parse();
+      new Parser(null, this, args.toList(growable: true)).parse();
 
   /**
    * Generates a string displaying usage information for the defined options.