dart2js: split out types from metadata.

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 4e19d86af118f38cce50c1521f350aed758d49e1..5a49cf12eeafc589c44493199f7a30e516a51753 100644
--- a/pkg/compiler/lib/src/js_emitter/model.dart
+++ b/pkg/compiler/lib/src/js_emitter/model.dart
@@ -55,6 +55,18 @@ class Program {
   /// data.
   List<String> get metadata => _metadataCollector.globalMetadata;
 
+  /// A list of pretty-printed JavaScript expressions.
+  ///
+  /// This list 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.
+  List<String> get metadataTypes => _metadataCollector.types;
+
   bool get isSplit => fragments.length > 1;
   Iterable<Fragment> get deferredFragments => fragments.skip(1);
 }