Created an `IsInterval` enum to improve readability and remove the need for `true // is_interval`
I'm still fairly new to rust. I briefly looked for a way to implement boolean comparisons of the enum but didn't figure out a way.
Also I'm not attached to any of the names. Let me know what I can fix :)
Source-Repo: https://github.com/servo/servo
Source-Revision: 90007ee781e53f65344a24a0bdbeb86d5c0fe065
#3050
Altough LayoutDataRef is touched from layout, we don't use DOMRefCell in it becasuse
it's expected to manipulate in layout task.
Source-Repo: https://github.com/servo/servo
Source-Revision: f5e8df9dac9330f2818906c471ed05f5975828c6