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

tests/compiler/dart2js/backend_dart/opt_constprop_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.
 
 import 'dart:async';
 import '../mock_compiler.dart';
 import 'sexpr_unstringifier.dart';
 import 'package:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
-import 'package:compiler/src/cps_ir/cps_ir_nodes_sexpr.dart';
-import 'package:compiler/src/cps_ir/optimizers.dart';
-import 'package:compiler/src/dart2jslib.dart' as dart2js;
+import 'package:compiler/implementation/cps_ir/cps_ir_nodes_sexpr.dart';
+import 'package:compiler/implementation/cps_ir/optimizers.dart';
+import 'package:compiler/implementation/dart2jslib.dart' as dart2js;
 
 // The tests in this file that ensure that sparse constant propagation on the
 // CPS IR works as expected.
 
 // CP1 represents the following incoming dart code:
 //
 //  int main() {
 //    int i = 1;
 //    int j;
 //    if (i == 1) {
@@ skipping 399 matching lines @@
   asyncTest(() => testConstantPropagator(CP2_IN, CP2_OUT));
   asyncTest(() => testConstantPropagator(CP3_IN, CP3_OUT));
   asyncTest(() => testConstantPropagator(CP4_IN, CP4_OUT));
   asyncTest(() => testConstantPropagator(CP5_IN, CP5_OUT));
   asyncTest(() => testConstantPropagator(CP6_IN, CP6_OUT));
   asyncTest(() => testConstantPropagator(CP7_IN, CP7_OUT));
   asyncTest(() => testConstantPropagator(CP8_IN, CP8_OUT));
   asyncTest(() => testConstantPropagator(CP9_IN, CP9_OUT));
   asyncTest(() => testConstantPropagator(CP10_IN, CP10_OUT));
 }