[AF Android] Maybe omit new dropdown in landscape mode

When the new dropdown is shown in landscape mode, most vertical space
is occupied with the on-screen keyboard and the sticky footer options,
leaving not enough space to actually show the suggestions.

This CL adds a quick fix that prevents the most common cases by
allowing the dropdown to only be shown in landscape mode when we are
sure that we have enough vertical space (e.g. tablets).

This will allow us to at least to experiment on the new dropdown in
M72 and collect metrics to understand the size of the affected
population and make an informed decision on how we should address
this issue.

Moving forward, the plan to properly fix this is:
 - [short term] Make the footer non-sticky;
 - [long term] Move away from the dropdown and show suggestions in the
   keyboard accessory.

A follow-up CL will add a new bucket to Autofill.FormEvents to track
how often that happens.

Bug: 905081
Change-Id: Ia8f8b14f987e13e8d9f0afc021d156fbf4238af6
Reviewed-on: https://chromium-review.googlesource.com/c/1346734
Commit-Queue: Fabio Tirelo <ftirelo@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613410}
4 files changed