[CrOS MultiDevice]: Handle and test subpage edge case.

I fixed a typo from the initial subpage CL that displayed the AWM
feature summary instead of SmartLock. Fixing this, however, required
handling a new case because SmartLock has a learn more link embedded in
its summary as well as a route to the LOCK_SCREEN settings subpage.

The issue is that clicking the link would open the link (as it should)
but also route the to the LOCK_SCREEN subpage because the click event
was propagated. In this CL I prevented the link from routing by
checking if the last element in the event's path was an <a> tag and, if
so, returning before routing.

I also added a test for the navigation behavior and simplified the
string localization by consolidating it in multidevice_subpage.html.

Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ie6c0f370bf345128ccda3f8d464e09b856b236a6
Reviewed-on: https://chromium-review.googlesource.com/1142518
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: Jordy Greenblatt <jordynass@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576604}
8 files changed