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

tests/compiler/dart2js/parser_test.dart

 // Copyright (c) 2011, 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.
 
 import "package:expect/expect.dart";
 import 'parser_helper.dart';
-import 'package:compiler/src/tree/tree.dart';
+import 'package:compiler/implementation/tree/tree.dart';
 
 void testStatement(String statement) {
   Node node = parseStatement(statement);
   Expect.isNotNull(node.toString());
 }
 
 void testGenericTypes() {
   testStatement('List<T> t;');
   testStatement('List<List<T>> t;');
   testStatement('List<List<List<T>>> t;');
@@ skipping 321 matching lines @@
   testWhileStatement();
   testConditionalExpression();
   testAssignment();
   testIndex();
   testPostfix();
   testOperatorParse();
   testMissingCloseParen();
   testMissingCloseBraceInClass();
   testUnmatchedAngleBracket();
 }