The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7cdb4669a382606ae5a4226e8bbc993992934507

commit 7cdb4669a382606ae5a4226e8bbc993992934507
Author: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Date: Tue Jan 23 20:58:18 2018

Revert "Enable V1app backbutton by default"

This reverts commit 304ec7f27e0a23583a04cb9d0888e328df253ac5.

Reason for revert:

The original patch enabled the back button on all Hosted App windows.
This included Desktop PWA Hosted Apps that had a manifest with
display:standalone which explicitly requests for no browser controls.

Reverting this change for now until we can disable the back button for
Desktop PWA Hosted Apps.

Original change's description:
> Enable V1app backbutton by default
> 
> Added about flag in case for troubleshooting.
> 
> BUG=749713
> TEST=manual
> 
> Change-Id: I2f74535282bb8dccca38a4d8ad6f10af88140c62
> Reviewed-on: https://chromium-review.googlesource.com/860522
> Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
> Reviewed-by: Michael Wasserman <msw@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#529074}

TBR=msw@chromium.org,oshima@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 749713,  804510 
Change-Id: I9d405002dc9061d42f4acb7575b4e7c08e8ce925
Reviewed-on: https://chromium-review.googlesource.com/874491
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#530382}(cherry picked from commit ca91b45e9052a21eceff60a32e8a31beabf5434e)
Reviewed-on: https://chromium-review.googlesource.com/881981
Cr-Commit-Position: refs/branch-heads/3325@{#36}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/ash/public/cpp/ash_switches.cc
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/ash/public/cpp/ash_switches.h
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/chrome/browser/about_flags.cc
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/chrome/browser/ui/views/frame/browser_non_client_frame_view_ash.cc
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/chrome/browser/ui/views/frame/browser_non_client_frame_view_ash.h
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/chrome/browser/ui/views/frame/browser_non_client_frame_view_ash_browsertest.cc
[modify] https://crrev.com/7cdb4669a382606ae5a4226e8bbc993992934507/tools/metrics/histograms/enums.xml