Avoid reparsing metadata expressions

pkg/compiler/lib/src/js_emitter/model.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.model;
 
 import '../js/js.dart' as js show Expression, Statement;
 import '../constants/values.dart' show ConstantValue;
 
 import '../deferred_load.dart' show OutputUnit;
@@ skipping 25 matching lines @@
           this.typeToInterceptorMap,
           this._metadataCollector,
           {this.needsNativeSupport,
            this.outputContainsConstantList,
            this.hasIsolateSupport}) {
     assert(needsNativeSupport != null);
     assert(outputContainsConstantList != null);
     assert(hasIsolateSupport != null);
   }
 
-  /// A list of pretty-printed JavaScript expressions.
+  /// A list of metadata expressions.
   ///
   /// This list must be emitted in the `METADATA` embedded global.
   /// The list references constants and must hence be emitted after constants
   /// have been initialized.
   ///
   /// Note: the metadata is derived from the task's `metadataCollector`. The
   /// list must not be emitted before all operations on it are done. For
   /// example, the old emitter generates metadata when emitting reflection
   /// data.
-  List<String> get metadata => _metadataCollector.globalMetadata;
+  List<js.Expression> get metadata => _metadataCollector.globalMetadata;
 
-  /// A map with lists of pretty-printed JavaScript expressions.
+  /// A map with lists of type expressions.
   ///
   /// There is one list for each output unit. The list belonging to the main
   /// unit must be emitted in the `TYPES` embedded global. The list references
   /// constants and must hence be emitted after constants have been initialized.
   ///
   /// Note: the metadata is derived from the task's `metadataCollector`. The
   /// list must not be emitted before all operations on it are done. For
   /// example, the old emitter generates metadata when emitting reflection
   /// data.
-  Map<OutputUnit, List<String>> get metadataTypes
+  Map<OutputUnit, List<js.Expression>> get metadataTypes
       => _metadataCollector.types;
 
 
   bool get isSplit => fragments.length > 1;
   Iterable<Fragment> get deferredFragments => fragments.skip(1);
   Fragment get mainFragment => fragments.first;
 }
 
 /**
  * This class represents a JavaScript object that contains static state, like
@@ skipping 402 matching lines @@
               requiredParameterCount: requiredParameterCount,
               optionalParameterDefaultValues: optionalParameterDefaultValues,
               functionType: functionType);
 }
 
 class StaticStubMethod extends StubMethod implements StaticMethod {
   Holder holder;
   StaticStubMethod(String name, this.holder, js.Expression code)
       : super(name, code);
 }