Add fieldtrial testing config for VisualFeaturesInPasswordProtectionAndroid

We are about to launch this to Beta, so add the fieldtrial_testing_config
entry for this experiment.

Bug: 1176352
Change-Id: Ibb4e8aa179f634ed43e25d3d206c23385233afe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2782085


Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#866182}