Implement MethodMirror.metadata.

dart/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 158 matching lines @@
       _jsVariableReserved.addAll(reservedPropertySymbols);
       _jsVariableReserved.addAll(reservedGlobalSymbols);
     }
     return _jsVariableReserved;
   }
 
   final String CURRENT_ISOLATE;
 
   final String getterPrefix = r'get$';
   final String setterPrefix = r'set$';
+  final String metadataField = '@';
 
   /**
    * Map from top-level or static elements to their unique identifiers provided
    * by [getName].
    *
    * Invariant: Keys must be declaration elements.
    */
   final Compiler compiler;
   final Map<Element, String> globals;
   final Map<String, LibraryElement> shortPrivateNameOwners;
@@ skipping 964 matching lines @@
     hash = hash ^ (hash >> 6);
     return hash;
   }
 
   static int _finish(int hash) {
     hash = _MASK & (hash + (((_MASK >> 3) & hash) <<  3));
     hash = hash & (hash >> 11);
     return _MASK & (hash + (((_MASK >> 15) & hash) << 15));
   }
 }