After discussion with felt@, we may want to increase the number of variations to simultaneously check:

- CONTROL: EV and Secure UI as-is.
- EV_REMOVAL: EV UI changed to match "Secure" verbose UI.
- SECURE_REMOVAL: "Secure" verbose UI downgraded to lock icon only. EV unchanged.
- LOCK_ONLY: EV UI and "Secure" verbose UI both downgraded to lock icon only.

I think this should be do-able all within the same trial gate code in LocationBarView.

I've started a CL for the multi-variant version of this: https://crrev.com/c/877400

+estark: What are your thoughts about the EV->Secure only version of this versus including variants for the additional UI changes?

The multiple variants plan sgtm!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d

commit 75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d
Author: Christopher Thompson <cthomp@chromium.org>
Date: Thu Feb 01 20:12:46 2018

Finch trial for EV/Secure chip UI reduction

This adds a new Finch variation changing the EV/Secure chip UI
(downgrading EV to Secure, downgrading Secure to Lock only, or downgrading
both to Lock only). It changes LocationBarView and LocationBarViewMac to
directly use ToolbarModel::GetSecureVerboseText(), and adds logic for
handling the experimental cases. It also adds browsertests for testing the
security levels and indicator text for the different variations.

Bug:  803508 
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I76014c18f0c2535766efd75d3eb2491cd7ab91c7
Reviewed-on: https://chromium-review.googlesource.com/877400
Commit-Queue: Christopher Thompson <cthomp@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533793}
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/about_flags.cc
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/ui/views/location_bar/location_bar_view.cc
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/ui/views/location_bar/location_bar_view.h
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/chrome/browser/ui/views/location_bar/location_bar_view_browsertest.cc
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/components/toolbar/BUILD.gn
[add] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/components/toolbar/toolbar_field_trial.cc
[add] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/components/toolbar/toolbar_field_trial.h
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/components/toolbar/toolbar_model_impl.cc
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/testing/buildbot/filters/mojo.fyi.network_browser_tests.filter
[modify] https://crrev.com/75ff845d89d0d3f48fc56cb9bd9f2cfe1e30bf7d/tools/metrics/histograms/enums.xml

I'll track the server-side config work in another task bug.