dart2js rti fix: functions are subtypes of Object

sdk/lib/_internal/js_runtime/lib/js_rti.dart

Index: sdk/lib/_internal/js_runtime/lib/js_rti.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/js_rti.dart b/sdk/lib/_internal/js_runtime/lib/js_rti.dart
index 91254ef2dad1901511974373cb340ff30e9d1793..f9cd6985f06bedc837c40f3ac4961bf4b436992b 100644
--- a/sdk/lib/_internal/js_runtime/lib/js_rti.dart
+++ b/sdk/lib/_internal/js_runtime/lib/js_rti.dart
@@ -452,9 +452,9 @@ bool isSubtype(var s, var t) {
   if (isDartFunctionType(t)) {
     return isFunctionSubtype(s, t);
   }
-  // Check function types against the Function class.
+  // Check function types against the Function class and the Object class.
   if (isDartFunctionType(s)) {
-    return isDartFunctionTypeRti(t);
+    return isDartFunctionTypeRti(t) || isDartObjectTypeRti(t);
   }
 
   // Get the object describing the class and check for the subtyping flag