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This CL adds ListBoxOption role as an item for Group role in
AXNode::SetRoleMatchesItemRole() since Group role could have
ListBoxOption as an item[1]. With this change, when the parent
of ListBoxOption is a group role, PosInSet and SetSize has
proper values.

[1]https://w3c.github.io/aria-practices/examples/listbox/listbox-grouped.html

Bug: 1066632
Change-Id: I23cf0c34ee479d6e8ee33b3f9e327def820527e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2134037
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756360}