Ignore adopted stylesheets from different document tree

If we adopt a subtree containing a shadowRoot that has
adoptedStyleSheets from one document to a different document, the
adoptedStyleSheets will be moved along with it. We want to ignore
the stylesheets that are constructed in a different document tree
when we're doing style calculation.

Draft spec: https://wicg.github.io/construct-stylesheets/

Bug: 807560
Change-Id: If36676e642b5d1b5c1c403c14cc24be8e670f153
Reviewed-on: https://chromium-review.googlesource.com/c/1377486
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616621}
3 files changed