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

tests/compiler/dart2js/type_variable_occurrence_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;
 
 void main() {
   testTypeVariableOccurrence();
 }
 
 testTypeVariableOccurrence() {
   asyncTest(() => TypeEnvironment.create(r"""
       typedef S Typedef1<S>();
       typedef void Typedef2<S>(S s);
@@ skipping 98 matching lines @@
     // void method5(A<T> t) {}
     expect(true, 'method5');
     // void method6(void foo(T t)) {}
     expect(true, 'method6');
     // void method7([T t]);
     expect(true, 'method7');
     // void method8({T t});
     expect(true, 'method8');
   }));
 }