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

tests/compiler/dart2js/js_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 'dart:async';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'mock_compiler.dart';
-import 'package:compiler/src/js/js.dart' as jsAst;
-import 'package:compiler/src/js/js.dart' show js;
+import 'package:compiler/implementation/js/js.dart' as jsAst;
+import 'package:compiler/implementation/js/js.dart' show js;
 
 Future testExpression(String expression, [String expect = ""]) {
   jsAst.Node node = js(expression);
   return MockCompiler.create((MockCompiler compiler) {
     String jsText =
         jsAst.prettyPrint(node,
                           compiler,
                           allowVariableMinification: false).getText();
     if (expect == "") {
       Expect.stringEquals(expression, jsText);
@@ skipping 164 matching lines @@
     testExpression("y = a == null ? b + c : a + c"),
     testExpression("foo = a ? b : c ? d : e"),
     testExpression("foo = a ? b ? c : d : e"),
     testExpression("foo = (a = v) ? b = w : c = x ? d = y : e = z"),
     testExpression("foo = (a = v) ? b = w ? c = x : d = y : e = z"),
     // Stacked assignment.
     testExpression("a = b = c"),
     testExpression("var a = b = c"),
   ]));
 }