Fix --expose-debug-as with number as argument.

test/mjsunit/regress/regress-crbug-405491.js

Index: test/mjsunit/regress/regress-crbug-405491.js
diff --git a/test/mjsunit/regress/regress-double-property.js b/test/mjsunit/regress/regress-crbug-405491.js
similarity index 79%
copy from test/mjsunit/regress/regress-double-property.js
copy to test/mjsunit/regress/regress-crbug-405491.js
index 2ddb45b4b66c79600c78abfaf5b64c1a9a13927a..b63378113f42a15b403d3884b14a97163ee53344 100644
--- a/test/mjsunit/regress/regress-double-property.js
+++ b/test/mjsunit/regress/regress-crbug-405491.js
@@ -2,8 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-function f(a) {
-  return {0.1: a};
-}
-
-f();
+// Flags: --expose-debug-as 1