Auto merge of #128 - servo:heapsize_plugin, r=SimonSapin
Auto merge of #128 - servo:heapsize_plugin, r=SimonSapin

Update heapsize_plugin



<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/rust-url/128)
<!-- Reviewable:end -->

servo/rust-url,servo/rust-url,cGuille/rust-url,cGuille/rust-url