Revert "Remove TypeToken as means for assigning type arguments to arrays."

compiler/lib/implementation/array.dart

 // Copyright (c) 2011, 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.
 
 class ListFactory<E> {
   factory List.from(Iterable<E> other) {
     if (other == null) {
       throw const NullPointerException();
     }
     List<E> list = new List<E>();
     for (final e in other) {
       list.add(e);
     }
     return list;
   }
 
   factory List([int length = null]) {
     bool isFixed = true;
     if (length === null) {
       length = 0;
       isFixed = false;
     } else if (length < 0) {
       throw new IllegalArgumentException("negative length $length");
     }
-    
-    ListImplementation<E> list = new ListImplementation<E>(length);
+    // TODO(floitsch): make list creation more efficient. Currently we allocate
+    // a new TypeToken at every allocation. Either we can optimize them away,
+    // or we need to find other ways to pass type-information from Dart to JS.
+    ListImplementation list = _new(new TypeToken<E>(), length);
     list._isFixed = isFixed;
     return list;
   }
+
+  static ListImplementation _new(TypeToken typeToken, int length) native;
 }
 
 
 class ListImplementation<T> implements List<T> native "Array" {
   // ListImplementation maps directly to a JavaScript array. If the list is
   // constructed by the ListFactory.List constructor, it has an
   // additional named property for '_isFixed'. If it is a literal, the
   // code generator will not add the property. It will be 'undefined'
   // and coerce to false.
   bool _isFixed;
 
-  ListImplementation(int length);
-  
   T operator[](int index) {
     if (0 <= index && index < length) {
       return _indexOperator(index);
     }
     throw new IndexOutOfRangeException(index);
   }
 
   void operator[]=(int index, T value) {
     if (index < 0 || length <= index) {
       throw new IndexOutOfRangeException(index);
@@ skipping 214 matching lines @@
   }
 
   static List _newList(int len) native {
     return new List(len);
   }
 
   static void _throwIndexOutOfRangeException(int index) native {
     throw new IndexOutOfRangeException(index);
   }
 }