Bug 1820788 [wpt PR 38850] - Use AdjustedFocusedElement when clearing focus from...

Bug 1820788 [wpt PR 38850] - Use AdjustedFocusedElement when clearing focus from children, a=testonly

Automatic update from web-platform-tests
Use AdjustedFocusedElement when clearing focus from children

In this case:

  <my-button>
    <template shadowrootmode=open>
      <button><slot></slot></button>
    </template>
    Button contents
  </my-button>

when the shadow root button is focused, calling
`myButton.textContent=''` clears the focus. This is due to a change made
for performance reasons in [1], but I think it's not the right behavior.
The focus should not be cleared in this case, since the adjusted focused
element is still the <my-button> element.

This CL goes back to using AdjustedFocusedElement. This might have
a negative perf impact, but I think it's important to not clear
focus for custom elements in this case.

[1] https://chromium.googlesource.com/chromium/src/+/9aab5fab831e4ce17a65d436c214deb650520355

Fixed: 1300584
Change-Id: I3c79dd41c92da9bd35d715bab56e2b8fdef50008
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4305572
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Commit-Queue: Mason Freed <masonf@chromium.org>
Auto-Submit: Mason Freed <masonf@chromium.org>
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1114311}

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wpt-commits: 14684f837eba364df3de2b6683d4eb5385333158
wpt-pr: 38850