remove unused allowConstCast option

test/checker/checker_test.dart

 // Copyright (c) 2015, 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.
 
 /// General type checking tests
 library dev_compiler.test.checker_test;
 
 import 'package:test/test.dart';
 
 import 'package:dev_compiler/src/testing.dart';
@@ skipping 1700 matching lines @@
             const A(num a) : this.fi = /*$error1*/a;
           }
           class B extends A {
             const B(Object a) : super(/*$error1*/a);
           }
           void foo(Object o) {
             var a = const A(/*$error1*/o);
           }
      ''';
     testChecker(
-        {'/main.dart': mk("severe:StaticTypeError", "severe:StaticTypeError")},
-        allowConstCasts: false);
-    testChecker(
-        {'/main.dart': mk("warning:DownCastImplicit", "info:AssignmentCast")},
-        allowConstCasts: true);
+        {'/main.dart': mk("warning:DownCastImplicit", "info:AssignmentCast")});
   });
 
   test('casts in conditionals', () {
     testChecker({
       '/main.dart': '''
           main() {
             bool b = true;
             num x = b ? 1 : 2.3;
             int y = /*info:AssignmentCast*/b ? 1 : 2.3;
             String z = !b ? "hello" : null;
@@ skipping 1296 matching lines @@
     '/main.dart': '''
       import 'dart:foobar' show Baz;
       main() {
         print(Baz.quux);
       }'''
   },
       customUrlMappings: {
     'dart:foobar': '$testDirectory/checker/dart_foobar.dart'
   }));
 }