Move dart2jslib parts into separate libraries.

tests/compiler/dart2js/semantic_visitor_test.dart

 // Copyright (c) 2015, 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.
 
 library dart2js.semantics_visitor_test;
 
 import 'dart:async';
 import 'dart:mirrors';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/dart_types.dart';
 import 'package:compiler/src/dart2jslib.dart';
 import 'package:compiler/src/elements/elements.dart';
+import 'package:compiler/src/messages.dart' show MessageKind;
 import 'package:compiler/src/resolution/resolution.dart';
 import 'package:compiler/src/resolution/semantic_visitor.dart';
 import 'package:compiler/src/resolution/operators.dart';
 import 'package:compiler/src/tree/tree.dart';
+import 'package:compiler/src/universe/universe.dart' show
+    CallStructure,
+    Selector;
 import 'package:compiler/src/util/util.dart';
 import 'memory_compiler.dart';
 
 part 'semantic_visitor_test_send_data.dart';
 part 'semantic_visitor_test_send_visitor.dart';
 part 'semantic_visitor_test_decl_data.dart';
 part 'semantic_visitor_test_decl_visitor.dart';
 
 class Visit {
   final VisitKind method;
@@ skipping 698 matching lines @@
   ERROR_INVALID_INDEX_SET,
   ERROR_INVALID_COMPOUND_INDEX_SET,
   ERROR_INVALID_INDEX_PREFIX,
   ERROR_INVALID_INDEX_POSTFIX,
 
   VISIT_CONSTANT_GET,
   VISIT_CONSTANT_INVOKE,
 
   PREVISIT_DEFERRED_ACCESS,
 }