My understanding of the desired search design:

1. chrome://md-settings - only Basic is visible
2. enter "setting" in search box
3. all sections disappear
4. as search progresses, each section with a match is shown, with matches
   highlighted

But the actual process differs from the above:

1. chrome://md-settings - only Basic is visible
2. enter "setting" in search box
3. the Advanced sections render below the Basic sections
4. the Basic sections disappear
5. as search progresses, sections in Basic with a match are shown, and
   sections in Advanced without a match are *eventually* hidden.

It ends up in the right state, but has the odd illusion of inserting sections in the middle of the page. See attached video for example. I slowed down search by adding a conditional breakpoint at the beginning of revealParentSection_:
    for (var i = 0; i < 2500; i++) console.log(i);
It never triggers, but evaluating it takes a long time ;-)