Fix implementation of Function.apply with optional positional arguments.

sdk/lib/_internal/compiler/js_lib/js_helper.dart

Index: sdk/lib/_internal/compiler/js_lib/js_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/js_helper.dart b/sdk/lib/_internal/compiler/js_lib/js_helper.dart
index 3b02cf27c88f0c8dd543bde9707c37ae274c37c1..9ef6d14e77864bb5f864f27495696a80f02aea12 100644
--- a/sdk/lib/_internal/compiler/js_lib/js_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/js_helper.dart
@@ -1181,7 +1181,7 @@ class Primitives {
       }
       arguments = new List.from(arguments);
       for (int pos = argumentCount; pos < maxArgumentCount; pos++) {
-        arguments.add(info.defaultValue(pos));
+        arguments.add(getMetadata(info.defaultValue(pos)));
       }
     }
     // We bound 'this' to [function] because of how we compile