dart2js: emit metadata in new emitter.

pkg/compiler/lib/src/js_emitter/model.dart

Index: pkg/compiler/lib/src/js_emitter/model.dart
diff --git a/pkg/compiler/lib/src/js_emitter/model.dart b/pkg/compiler/lib/src/js_emitter/model.dart
index 1c3f80d72cbbf1e8885d7ab12b17cb6ece405431..248a7b85c25a322f57ea85f2ec768a573036707d 100644
--- a/pkg/compiler/lib/src/js_emitter/model.dart
+++ b/pkg/compiler/lib/src/js_emitter/model.dart
@@ -9,6 +9,8 @@ import '../constants/values.dart' show ConstantValue;
 
 import '../deferred_load.dart' show OutputUnit;
 
+import 'js_emitter.dart' show MetadataCollector;
+
 import '../common.dart';
 
 class Program {
@@ -22,15 +24,34 @@ class Program {
   // global `TYPE_TO_INTERCEPTOR_MAP`. The map references constants and classes.
   final js.Expression typeToInterceptorMap;
 
+  // TODO(floitsch): we should store the metadata directly instead of storing
+  // the collector. However, the old emitter still updates the data.
+  final MetadataCollector _metadataCollector;
+
   Program(this.fragments,
           this.loadMap,
           this.typeToInterceptorMap,
+          this._metadataCollector,
           {this.outputContainsNativeClasses,
            this.outputContainsConstantList}) {
     assert(outputContainsNativeClasses != null);
     assert(outputContainsConstantList != null);
   }
 
+  /// A list of pretty-printed JavaScript expressions.
+  ///
+  /// This list must be emitted in the `METADATA` embedded global.
+  /// References to classes or constants are wrapped into functions (that are

[floitsch, 2015/01/29 17:06:31]

I'm not yet 100% sure of these claims. If necessary I will update the comment
once I run into data that behaves differently.

[floitsch, 2015/01/29 17:12:18]

Already updated...

+  /// only executed at runtime). It is safe to emit the data before classes
+  /// and constants are completely set up. In fact, the data must be emitted
+  /// before any class (including constant) is constructed.
+  ///
+  /// 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;
+
   bool get isSplit => fragments.length > 1;
   Iterable<Fragment> get deferredFragments => fragments.skip(1);
 }