I have added an update note to the post. Also, I have added a table comparison between polymorphic & non-polymorphic runs.
I will fix the code to use pseudo-random function to make the test results more meaningful.Also, I will try to send a pull request to the original test author.
Yes, other engines do not seem to handle polymorphism well. I just amended the code to use separate test_something_arraytype for each array type. And, it turns out that the performance of other browsers have improved significantly and they look closer to Chrome now. Check out the updated charts in the blog post.