Add shadowRootDelegatesFocus and shadowRootClonable reflection
The `shadowRootDelegatesFocus` IDL is standardized [1], and was just
never added to Chromium. This CL lands this addition behind a kill
switch, but should be very safe to add.
The `shadowRootClonable` IDL is being added as part of [2], which
has support and should land soon.
[1] https://html.spec.whatwg.org/multipage/scripting.html#htmltemplateelement
[2] https://github.com/whatwg/html/pull/10117
Bug: 1510466
Change-Id: I708ec8d562fa4d0fc59c73a071dbb191e1bd276e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5261148
Commit-Queue: Mason Freed <masonf@chromium.org>
Reviewed-by: David Baron <dbaron@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1260805}
