disable_with does not work with Safari

I have the following in Rails 4.2.

`<%= link_to "Add new post", new_post_path, data: { disable_with: "Please wait..." } %>`

Tested on other browser is fine except Safari. On Safari, it doesn't change the text to `Please wait...`, and is still clickable multiple times and fire to controller multiple times.

Reproduce the Safari behavior using the Rails 4.2 link_to example with data-disable-with, then trace the disable_with handling in vanilla-ujs. Done means the link changes to “Please wait...” and repeated clicks do not fire the controller multiple times in Safari, while existing browser behavior remains intact.

Written by the indexing model from the issue text.