merge_pr_60231

[focusgroup] Align ParseFocusgroup with latest spec draft

Align the focusgroup attribute parsing with the formal "determine the
focusgroup state" algorithm defined in the HTML spec PR:
whatwg/html#11723.

With this change, "none" and the behavior token can appear at any
position. Before, the these were required to be the first token or
parsing would fire an error.

Bug: 4021071
Change-Id: Ic258d4fc39f9850c5cabac2b4afa0dbcf6c32d95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7871960
Commit-Queue: Jacques Newman janewman@microsoft.com
Reviewed-by: Mason Freed masonf@chromium.org
Cr-Commit-Position: refs/heads/main@{#1637192}