servo: Merge #5693 - Add/update comments with links to spec (from frewsxcv:spec-links); r=jdm

Extracted out of #5649

* add more hyperlinks to associated specification for structs/methods
* follow redirects and update links
* replace broken links
* removal of WHATWG multipage page name since the page name is not
  guaranteed to be stable

Source-Repo: https://github.com/servo/servo
Source-Revision: 3dc25af9e121db010e4385efb3863ba45b0e0bcf

servo/components/script/dom/canvaspattern.rs

@@ -4,6 +4,7 @@
 
 use dom::bindings::utils::Reflector;
 
+// https://html.spec.whatwg.org/multipage/#canvaspattern
 #[dom_struct]
 pub struct CanvasPattern {
     reflector_: Reflector,