I think best practice is to also have a kill switch via Finch to disable any server-related features in case of accidental DoS on our own servers. (That would be regardless of user enabled state.)

I'll do this

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/33d6dc519bd369a51953e47cf072e93282ba5a4f

commit 33d6dc519bd369a51953e47cf072e93282ba5a4f
Author: yfriedman <yfriedman@chromium.org>
Date: Tue Aug 16 23:29:12 2016

Add an about:flag to control WebApk enablement.

- Moves it out from being only a command line flag.
- Adds a finch override (kill switch)
- Centralizes logic in ChromeWebApkHost and caches configuration
in a shared pref so that it can be read before native is loaded.
BUG= 633803 

Review-Url: https://codereview.chromium.org/2242473002
Cr-Commit-Position: refs/heads/master@{#412372}

[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/init/ChromeBrowserInitializer.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/notifications/NotificationPlatformBridge.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/preferences/ChromePreferenceManager.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/android/javatests/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandlerTest.java
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/app/generated_resources.grd
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/browser/about_flags.cc
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/browser/android/shortcut_helper.cc
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/chrome/browser/notifications/notification_platform_bridge_android.cc
[modify] https://crrev.com/33d6dc519bd369a51953e47cf072e93282ba5a4f/tools/metrics/histograms/histograms.xml