Fix typechecks for constant assignments of function to typedefs.

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 36ddfa55cd3ca54374ce24368dfc1ac24e4d4d9a..ba4c74f52806cf18ecee83cd65e0922140582f5a 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -666,7 +666,9 @@ class JavaScriptBackend extends Backend {
 
   void registerInstantiatedConstantType(DartType type, TreeElements elements) {
     Enqueuer enqueuer = compiler.enqueuer.codegen;
-    enqueuer.registerInstantiatedType(type, elements);
+    DartType instantiatedType =
+        type.kind == TypeKind.FUNCTION ? compiler.functionClass.rawType : type;
+    enqueuer.registerInstantiatedType(instantiatedType, elements);
     if (type is InterfaceType && !type.treatAsRaw &&
         classNeedsRti(type.element)) {
       enqueuer.registerStaticUse(getSetRuntimeTypeInfo());