app-URI spec compliance tests
Order is apparently wrong making the test fail.

Based on my understanding of the tabindex behavior as explained in the
html5 living standard: pre-order, depth first tree order ("before any
element whose tabindex attribute has a value equal to the value of the
tabindex attribute on the element but that is later in the document in
tree order than the element").
Wrong order for some nodes unrelated to shadow dom

The expected order of nodes outside of the shadow root was wrong. Since
there is no identical tabindex in use, the order is simply tabindex.
"before any element whose tabindex attribute has a value greater than
the value of the tabindex attribute on the element."
add Shadow root olderShadowRoot Attributes test
read-write, read-only test
Fixed textarea content and input element description
Add URL IDL tests & drop stale (untested) URL IDLs

This change:

  [x] adds URL & URLUtils* IDL tests (up-to-date with current URL spec)
  [x] drops untested URL & URLUtils* IDLs from html/dom/interfaces.html
  [x] replaces old untested html/dom/interfaces.html URLUtils* IDLs w/ stubs

(Nothing in html/dom/interfaces.html references the URL interface anyway,
so there's no reason to include it there. And the URLUtils* IDLs that were
in there were out-of-date with the current URL spec, and regardless there's
no need to include the actual whole interfaces for them there, so instead
let's just put (untested) stubs for them there.)
read-write can't match disabled input elements
[çc] Add conformance-checker tests for <picture>
Remove .DS_Store
Test 1x and 1.0x
Add some srcset/sizes tests with empty value, single comma, multiple commas
Updated the text in paragraph since it was incorrect and irrelevant
Fix review comments
Add some tests for missing srcset on source
Fix review comments
Add a test with /**/ in srcset
Fix trailing css comment test
Fix aria region test name
Ban role=presentation