Implement ClassMirror.metadata.

dart/sdk/lib/_internal/compiler/implementation/lib/js_mirrors.dart

Index: dart/sdk/lib/_internal/compiler/implementation/lib/js_mirrors.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/lib/js_mirrors.dart b/dart/sdk/lib/_internal/compiler/implementation/lib/js_mirrors.dart
index 8e253dabd4ae6dc13420e0a510fad9de751aa0a1..d1f93eda316292825eb33fe4bc80b97ffa78164c 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/lib/js_mirrors.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/lib/js_mirrors.dart
@@ -262,6 +262,7 @@ class JsClassMirror extends JsObjectMirror implements ClassMirror {
   final Symbol simpleName;
   final _jsConstructor;
   final String _fields;
+  List _metadata;
   // Set as side-effect of accessing JsLibraryMirror.classes.
   JsLibraryMirror _owner;
 
@@ -370,6 +371,15 @@ class JsClassMirror extends JsObjectMirror implements ClassMirror {
     return _owner;
   }
 
+  List<InstanceMirror> get metadata {
+    if (_metadata == null) {
+      var metadataFunction = JS('', '#.prototype["@"]', _jsConstructor);
+      _metadata = (metadataFunction == null)
+          ? const [] : JS('', '#()', metadataFunction);
+    }
+    return _metadata.map(reflect).toList();
+  }
+
   String toString() => 'ClassMirror(${n(simpleName)})';
 }