Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

tests/compiler/dart2js/type_order_test.dart

 // Copyright (c) 2013, 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.
 
 library subtype_test;
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'type_test_helper.dart';
-import 'package:compiler/implementation/dart_types.dart';
-import "package:compiler/implementation/elements/elements.dart"
+import 'package:compiler/src/dart_types.dart';
+import "package:compiler/src/elements/elements.dart"
        show Element, ClassElement, TypedefElement;
 
 void main() {
   asyncTest(() => TypeEnvironment.create(r"""
       class A<AT, AS> {}
       typedef BS B<BT, BS>(BT t);
       class C<CT, CS> extends A<CS, CT> {}
       class X {}
       class Y {}
       class Z {}
@@ skipping 41 matching lines @@
         [void_, dynamic_,
          A_raw, A_this, A_X_Y, A_Y_X, AT, AS,
          B_raw, B_this, B_X_Y, B_Y_X, BT, BS,
          C_raw, C_this, CT, CS,
          X, Y, Z,
          B_this_alias, B_Y_X_alias, B_X_Y_alias,
         ],
         Types.sorted(types));
   }));
 }