Change js_emitter parts into libraries

pkg/compiler/lib/src/js_emitter/main_call_stub_generator.dart

Index: pkg/compiler/lib/src/js_emitter/main_call_stub_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/main_call_stub_generator.dart b/pkg/compiler/lib/src/js_emitter/main_call_stub_generator.dart
index d104cd492078bd364fc10aee2eae97467890d50c..36a305cf9affbb4f9ca5359de683dff6815cb9d2 100644
--- a/pkg/compiler/lib/src/js_emitter/main_call_stub_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/main_call_stub_generator.dart
@@ -2,7 +2,22 @@
 // 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.
 
-part of dart2js.js_emitter;
+library dart2js.js_emitter.main_call_stub_generator;
+
+import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
+
+import '../compiler.dart' show Compiler;
+import '../elements/elements.dart'
+    show
+    Element;
+import '../js/js.dart' as jsAst;
+import '../js/js.dart' show js;
+import '../js_backend/backend_helpers.dart' show BackendHelpers;
+import '../js_backend/js_backend.dart'
+    show
+    JavaScriptBackend;
+
+import 'code_emitter_task.dart' show CodeEmitterTask;
 
 class MainCallStubGenerator {
   final Compiler compiler;