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

tests/compiler/dart2js/js_spec_string_test.dart

 // Copyright (c) 2014, 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.
 
 // Unit test of the [NativeBehavior.processSpecString] method.
 
 import 'package:expect/expect.dart';
-import 'package:compiler/implementation/native/native.dart';
-import 'package:compiler/implementation/dart2jslib.dart'
+import 'package:compiler/src/native/native.dart';
+import 'package:compiler/src/dart2jslib.dart'
     show DiagnosticListener;
 
 const OBJECT = 'Object';
 const NULL = 'Null';
 
 class Listener implements DiagnosticListener {
   String errorMessage;
   internalError(spannable, message) => errorMessage = message;
 
   noSuchMethod(_) => null;
@@ skipping 47 matching lines @@
   test('returns:void;creates:A;', returns: [], creates: ['A']);
   test('returns:;creates:A|B;', returns: [OBJECT, NULL], creates: ['A', 'B']);
   test('returns:var;creates:A|B|C;',
       returns: [OBJECT, NULL], creates: ['A', 'B', 'C']);
   test('returns:A; creates:A|B|C; ', returns: ['A'], creates: ['A', 'B', 'C']);
   test(' returns:A|B;  creates:A|C;',
       returns: ['A', 'B'], creates: ['A', 'C']);
   test(' returns:A|B|C;   creates:A;  ',
       returns: ['A', 'B', 'C'], creates: ['A']);
 }