Use shorter names for some standard properties on closures.

pkg/compiler/lib/src/js_backend/frequency_namer.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.
 
 part of js_backend.namer;
 
 class FrequencyBasedNamer extends Namer
     with _MinifiedFieldNamer, _MinifiedOneShotInterceptorNamer
     implements jsAst.TokenFinalizer {
   _FieldNamingRegistry fieldRegistry;
   List<TokenName> tokens = new List<TokenName>();
 
   Map<NamingScope, TokenScope> _tokenScopes =
       new Maplet<NamingScope, TokenScope>();
 
   // Some basic settings for smaller names
   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;
 
   final String getterPrefix = 'g';
   final String setterPrefix = 's';
   final String callPrefix = ''; // this will create function names $<n>
+  String get requiredParameterField => r'$R';
+  String get defaultValuesField => r'$D';
+  String get operatorSignature => r'$S';
 
   jsAst.Name get staticsPropertyName =>
       _staticsPropertyName ??= getFreshName(instanceScope, 'static');
 
   FrequencyBasedNamer(NativeData nativeData, ClosedWorld closedWorld,
       CodegenWorldBuilder codegenWorldBuilder)
       : super(nativeData, closedWorld, codegenWorldBuilder) {
     fieldRegistry = new _FieldNamingRegistry(this);
   }
 
@@ skipping 99 matching lines @@
     String proposal;
     do {
       proposal = new String.fromCharCodes(_nextName);
       _incrementName();
     } while (MinifyNamer._hasBannedPrefix(proposal) ||
         illegalNames.contains(proposal));
 
     return proposal;
   }
 }