Fix null.runtimeType, reflect(null).type.superinterfaces, and reflect(null).getField.

sdk/lib/_internal/compiler/implementation/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer implements ClosureNamer {
@@ skipping 721 matching lines @@
     } else if (cls == backend.jsNumberClass) {
       return 'num';
     } else if (cls == backend.jsBoolClass) {
       return 'bool';
     } else if (cls == backend.jsDoubleClass) {
       return 'double';
     } else if (cls == backend.jsStringClass) {
       return 'String';
     } else if (cls == backend.jsArrayClass) {
       return 'List';
+    } else if (cls == backend.jsNullClass) {
+      return 'Null';
     } else {
       return null;
     }
   }
 
   /**
    * Returns a preferred JS-id for the given element. The returned id is
    * guaranteed to be a valid JS-id. Globals and static fields are furthermore
    * guaranteed to be unique.
    *
@@ skipping 641 matching lines @@
         if (!first) {
           sb.write('_');
         }
         sb.write('_');
         visit(link.head);
         first = true;
       }
     }
   }
 }