Change js_emitter parts into libraries

pkg/compiler/lib/src/js_emitter/main_call_stub_generator.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.
 
-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;
   final JavaScriptBackend backend;
   final CodeEmitterTask emitterTask;
 
   MainCallStubGenerator(this.compiler, this.backend, this.emitterTask);
 
   BackendHelpers get helpers => backend.helpers;
 
@@ skipping 62 matching lines @@
         } else {
           #mainCallClosure([]);
         }
       })''',
         {
           'currentScript': currentScriptAccess,
           'mainCallClosure': mainCallClosure
         });
   }
 }