Put back optimization on fixed-size array.

tests/compiler/dart2js/value_range_test.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.
 
 import 'compiler_helper.dart';
 
 const int REMOVED = 0;
 const int ABOVE_ZERO = 1;
 const int BELOW_LENGTH = 2;
 const int KEPT = 3;
@@ skipping 193 matching lines @@
 const String DEFAULT_CORELIB_WITH_LIST_INTERFACE = r'''
   print(var obj) {}
   abstract class num {}
   abstract class int extends num { }
   abstract class double extends num { }
   class bool {}
   class String {}
   class Object {}
   class Type {}
   class Function {}
-  interface List default ListImplementation { List([length]);}
-  class ListImplementation { factory List([length]) => null; }
+  class List { List([length]); }
   abstract class Map {}
   class Closure {}
   class Null {}
   class Dynamic_ {}
   bool identical(Object a, Object b) {}''';
 
 expect(String code, int kind) {
   String generated =
       compile(code, coreSource: DEFAULT_CORELIB_WITH_LIST_INTERFACE);
   switch (kind) {
@@ skipping 29 matching lines @@
       break;
   }
 }
 
 
 main() {
   for (int i = 0; i < TESTS.length;  i += 2) {
     expect(TESTS[i], TESTS[i + 1]);
   }
 }