Make 'click' the default action of unfocusable ARIA buttons

Users of ATs on AuraLinux use the default action to know whether or not
to activate nodes via the keyboard or a simulated mouse event. When a
node with a button role cannot receive keyboard focus, have the default
action be click. This heuristic helps ensure that when there is an ARIA
button that cannot be activated via the keyboard, users know to simulate
a mouse click.

Bug: 1025264
Change-Id: I8f7a79144ba88ef154eb10ead8dd991aed0d659d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1940331
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Joanmarie Diggs <jdiggs@igalia.com>
Cr-Commit-Position: refs/heads/master@{#722165}
7 files changed