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

tests/compiler/dart2js/type_combination_test.dart

 // Copyright (c) 2012, 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:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 import "compiler_helper.dart";
-import "package:compiler/implementation/types/types.dart";
+import "package:compiler/src/types/types.dart";
 import "type_mask_test_helper.dart";
-import 'package:compiler/implementation/js_backend/js_backend.dart';
+import 'package:compiler/src/js_backend/js_backend.dart';
 
 TypeMask nullType;
 TypeMask objectType;
 TypeMask jsBoolean;
 TypeMask jsNumber;
 TypeMask jsInteger;
 TypeMask jsDouble;
 TypeMask jsBooleanOrNull;
 TypeMask jsNumberOrNull;
 TypeMask jsIntegerOrNull;
@@ skipping 715 matching lines @@
         compiler.objectClass, world);
     emptyType = const TypeMask.nonNullEmpty();
     dynamicType = new TypeMask.subclass(
         compiler.objectClass, world);
 
     testUnion(compiler);
     testIntersection(compiler);
     testRegressions(compiler);
   }));
 }