Emit declarations for typedefs that are needed by reflection.

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index 1b6ca007e6b3bcca2b78d518acbe003a0ae82fbf..b1ee024886738434fd19a09ed126fb074e265ac0 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -340,9 +340,6 @@ class JavaScriptBackend extends Backend {
   /// List of elements that the backend may use.
   final Set<Element> helpersUsed = new Set<Element>();
 
-  /// Set of typedefs that are used as type literals.
-  final Set<TypedefElement> typedefTypeLiterals = new Set<TypedefElement>();
-
   /// All the checked mode helpers.
   static const checkedModeHelpers = CheckedModeHelper.helpers;
 
@@ -1937,11 +1934,13 @@ class JavaScriptBackend extends Backend {
     if (foundClosure) {
       reflectableMembers.add(closureClass);
     }
-    // It would be nice to have a better means to select
     Set<Element> closurizedMembers = compiler.resolverWorld.closurizedMembers;
     if (closurizedMembers.any(reflectableMembers.contains)) {
       reflectableMembers.add(boundClosureClass);
     }
+    // Add typedefs.
+    reflectableMembers
+        .addAll(compiler.world.allTypedefs.where(referencedFromMirrorSystem));
     // Register all symbols of reflectable elements
     for (Element element in reflectableMembers) {
       symbolsUsed.add(element.name);
@@ -2170,7 +2169,7 @@ class JavaScriptionResolutionCallbacks extends ResolutionCallbacks {
     // when reflection is used.  However, as long as we disable tree-shaking
     // eagerly it doesn't matter.
     if (type.isTypedef) {
-      backend.typedefTypeLiterals.add(type.element);
+      backend.compiler.world.allTypedefs.add(type.element);
     }
     backend.customElementsAnalysis.registerTypeLiteral(type, registry);
   }