dart2js: compile metadata lazily in the lazy emitter.

pkg/compiler/lib/src/js_emitter/new_emitter/emitter.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.
 
 library dart2js.new_js_emitter.emitter;
 
 import 'package:_internal/compiler/js_lib/shared/embedded_names.dart' show
     JsBuiltin,
     METADATA,
     TYPES;
@@ skipping 153 matching lines @@
         return _backend.rti.representationGenerator
             .templateForCreateFunctionType;
 
       case JsBuiltin.isSubtype:
         // TODO(floitsch): move this closer to where is-check properties are
         // built.
         String isPrefix = namer.operatorIsPrefix;
         return js.js.expressionTemplateFor("('$isPrefix' + #) in #.prototype");
 
       case JsBuiltin.getMetadata:
-        String metadataAccess =
-            _emitter.generateEmbeddedGlobalAccessString(METADATA);
-        return js.js.expressionTemplateFor("$metadataAccess[#]");
+        return _emitter.templateForReadMetadata;
 
       case JsBuiltin.getType:
         return _emitter.templateForReadType;
 
       default:
         _compiler.internalError(NO_LOCATION_SPANNABLE,
                                 "Unhandled Builtin: $builtin");
         return null;
     }
   }
 
   @override
   void invalidateCaches() {
   }
 }