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

tests/compiler/dart2js/type_representation_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/js/js.dart';
-import 'package:compiler/implementation/elements/elements.dart'
+import 'package:compiler/src/dart_types.dart';
+import 'package:compiler/src/js/js.dart';
+import 'package:compiler/src/elements/elements.dart'
        show Element, ClassElement;
-import 'package:compiler/implementation/js_backend/js_backend.dart'
+import 'package:compiler/src/js_backend/js_backend.dart'
        show JavaScriptBackend, TypeRepresentationGenerator;
 
 void main() {
   testTypeRepresentations();
 }
 
 void testTypeRepresentations() {
   asyncTest(() => TypeEnvironment.create(r"""
       typedef void Typedef();
       typedef int Typedef2();
@@ skipping 220 matching lines @@
 
     // m10(void f(int a, [b])) {}
     expect(env.getElement('m10').computeType(env.compiler),
            '{$func: "dynamic__void__int__dynamic", $args:'
            ' [{$func: "void__int__dynamic",'
            ' $retvoid: true, $args: [$int_rep], $opt: [null]}]}');
   }));
 }