https://www.chromestatus.com/metrics/feature/timeline/popularity/2535

The usage is very low.  I think we may change the behavior without intent process.

I would like to work on it if nobody is working yet.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2010bba41812ac1f3ea92a286c3894a14535766e

commit 2010bba41812ac1f3ea92a286c3894a14535766e
Author: Amos Lim <eui-sang.lim@samsung.com>
Date: Tue Oct 30 04:33:24 2018

Forms: Remove delegation of focus on legend

legend.focus() should not delegate focus.

Bug: https://github.com/whatwg/html/issues/3950
Bug:  880026 
Change-Id: I35e046e45bbc45628f148383eaa77f12245e9e98
Reviewed-on: https://chromium-review.googlesource.com/c/1304180
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Amos Lim <eui-sang.lim@samsung.com>
Cr-Commit-Position: refs/heads/master@{#603783}
[delete] https://crrev.com/be93f1261844787778e0c1ae4efa36bc3d763311/third_party/WebKit/LayoutTests/external/wpt/html/interaction/focus/processing-model/legend-expected.txt
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/WebKit/LayoutTests/fast/forms/access-key-expected.txt
[delete] https://crrev.com/be93f1261844787778e0c1ae4efa36bc3d763311/third_party/WebKit/LayoutTests/fast/forms/fieldset/legend-access-key-expected.txt
[delete] https://crrev.com/be93f1261844787778e0c1ae4efa36bc3d763311/third_party/WebKit/LayoutTests/fast/forms/fieldset/legend-access-key.html
[delete] https://crrev.com/be93f1261844787778e0c1ae4efa36bc3d763311/third_party/WebKit/LayoutTests/fast/forms/fieldset/legend-focus.html
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/WebKit/LayoutTests/fast/forms/focus-expected.txt
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/WebKit/LayoutTests/fast/forms/focus-selection-input-expected.txt
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/WebKit/LayoutTests/fast/forms/focus-selection-input.html
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/WebKit/LayoutTests/fast/forms/focus-selection-textarea-expected.txt
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/WebKit/LayoutTests/fast/forms/focus.html
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/blink/public/platform/web_feature.mojom
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/blink/renderer/core/html/forms/html_legend_element.cc
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/third_party/blink/renderer/core/html/forms/html_legend_element.h
[modify] https://crrev.com/2010bba41812ac1f3ea92a286c3894a14535766e/tools/metrics/histograms/enums.xml