Revert "Parts must start with 'part of'" and "Attempt to fix VM build"

dart/lib/compiler/implementation/lib/js_helper.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.
 
-library js_helper;
+#library('dart:_js_helper');
 
-import 'dart:coreimpl';
+#import('dart:coreimpl');
 
-part 'constant_map.dart';
-part 'native_helper.dart';
-part 'regexp_helper.dart';
-part 'string_helper.dart';
+#source('constant_map.dart');
+#source('native_helper.dart');
+#source('regexp_helper.dart');
+#source('string_helper.dart');
 
 // Performance critical helper methods.
 add(var a, var b) => (a is num && b is num)
     ? JS('num', r'# + #', a, b)
     : add$slow(a, b);
 
 sub(var a, var b) => (a is num && b is num)
     ? JS('num', r'# - #', a, b)
     : sub$slow(a, b);
 
@@ skipping 1378 matching lines @@
     JS('void', r'#.runtimeTypeCache[#] = #', JS_CURRENT_ISOLATE(), key,
        runtimeType);
   }
   return runtimeType;
 }
 
 String getRuntimeTypeString(var object) {
   var typeInfo = JS('Object', r'#.builtin$typeInfo', object);
   return JS('String', r'#.runtimeType', typeInfo);
 }