The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0b2aeaccf0023facc1ba07bd953f535225138386

commit 0b2aeaccf0023facc1ba07bd953f535225138386
Author: pkotwicz <pkotwicz@chromium.org>
Date: Tue Nov 08 03:32:52 2016

Show AlertDialog when WebAPKs are enabled in chrome://flags but Unknown sources is disabled

This CL also adds caching for whether the --enable-webapk command line flag is
set. The goal of the caching is to avoid showing the AlertDialog when the
variation state changes

BUG= 661712 

Review-Url: https://codereview.chromium.org/2472073003
Cr-Commit-Position: refs/heads/master@{#430503}

[modify] https://crrev.com/0b2aeaccf0023facc1ba07bd953f535225138386/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
[modify] https://crrev.com/0b2aeaccf0023facc1ba07bd953f535225138386/chrome/android/java/src/org/chromium/chrome/browser/preferences/ChromePreferenceManager.java
[modify] https://crrev.com/0b2aeaccf0023facc1ba07bd953f535225138386/chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java
[modify] https://crrev.com/0b2aeaccf0023facc1ba07bd953f535225138386/chrome/android/java/strings/android_chrome_strings.grd

Steps for test team:
1) In Android Settings > Security, disable "installation from Unknown sources"
2) In Android Settings > Apps, "Force Stop" Chrome
3) Navigate to chrome://flags
4) Enable "Improved add to Home screen"
5) Tap the "Relaunch Now" button
6) Check that the an alert dialog is displayed instructing the user to "Enable installation from Unknown sources"