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

runtime/lib/array_patch.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.
 
 // Note that the optimizing compiler depends on the algorithm which
 // returns a _GrowableObjectArray if length is null, otherwise returns
 // fixed size array.
 patch class List<E> {
-  /* patch */ factory List([int length = 0]) {
+  /* patch */ factory List([int length]) {
+    if (!?length) return new _GrowableObjectArray<E>(0);
     if ((length is! int) || (length < 0)) {

[Ivan Posva, 2013/02/27 18:14:36]

Why do we still do manual type checking here?

[floitsch, 2013/02/28 09:41:58]

1) because we didn't go through code to remove checks.
2) we do this check in dart2js, to avoid passing something bad to JS. This way
these two implementations are consistent.

       _throwArgumentError(length);
     }
-    _GrowableObjectArray<E> result = new _GrowableObjectArray<E>(length);
+    _ObjectArray<E> result = new _ObjectArray<E>(length);
     return result;
   }
 
-  /* patch */ factory List.fixedLength(int length, {E fill: null}) {
+  /* patch */ factory List.filled(int length, E fill) {
     if ((length is! int) || (length < 0)) {
       _throwArgumentError(length);
     }
     _ObjectArray<E> result = new _ObjectArray<E>(length);
     if (fill != null) {
       for (int i = 0; i < length; i++) {
         result[i] = fill;
       }
     }
     return result;
   }
 
   // Factory constructing a mutable List from a parser generated List literal.
   // [elements] contains elements that are already type checked.
   factory List._fromLiteral(List elements) {
     if (elements.isEmpty) {
       return new _GrowableObjectArray<E>(0);
     }
     var result = new _GrowableObjectArray<E>.withData(elements);
     result._setLength(elements.length);
     return result;
   }
 
   static void _throwArgumentError(int length) {
     throw new ArgumentError("Length must be a positive integer: $length.");
   }
 }