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This CL adds a new component <cr-menu-selector> that takes in a set of
elements that have a role of 'menuitem' and manages focus between the
items as the user uses arrow, Home, and End keys. The first menuitem
is the only menuitem that is focusable using the Tab key, allowing users
to easily skip over the menu to the main content area of a page.

This follows the accessibility guidelines set for navigation drawers.
This element will also be used on the History page's menu.

Bug: 1110405
Change-Id: I1d644959412d5c19f324d75336bd0e9a08ce7ca1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2436706Reviewed-by: dpapad <dpapad@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814293}