GitLab

This roughly halves(!) the number of active layers (per
Compositing.Browser.NumActiveLayers) on platforms where FocusRings are
enabled (Mac). This is due to FocusRing previously always painting on
layers regardless of there being anything to draw or not (e.g. it was
always an early return in ::OnPaint rather than preventing the layer
paint).

Bug: chromium:924232
Change-Id: If7b9fcfa2f24b42f2c9b2e86b1b2f1543908b7a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1902066
Auto-Submit: Peter Boström <pbos@chromium.org>
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Reviewed-by: Collin Baker <collinbaker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713254}