Steps to reproduce the problem:
PWAs can be launched to fullscreen via an inlined intent uri. 
1) Take a working intent from another device, copy it to your device, launch
2) PWA won't launch because the org.chromium.chrome.browser.webapp_mac is unknown to the browser

OR

1) launch a standalone webapp via an inlined intent uri without adding org.chromium.chrome.browser.webapp_mac to the intent

What is the expected behavior?
It should be possible to pre-install and launch PWAs in a managed device setting mandating user involvement

What went wrong?
PWA won't start. Further details in the "An Aside: Provisioning a PWA home screen icon" section:
https://developer.zebra.com/community/android/android-forums/android-blogs/blog/2016/11/13/progressive-web-applications-in-the-enterprise 

and

http://stackoverflow.com/questions/29103192/start-chrome-as-web-app-on-android-start#30349889

Did this work before? No 

Does this work in other browsers? N/A

Chrome version: 54.0.2840.98  Channel: stable
OS Version: Android 4.4.x
Flash Version: 

we want to launch a standalone PWA via an inlined intent uri that was preinstalled to the device. the per-device token in org.chromium.chrome.browser.webapp_mac, which has to be added to the intent, forbids this.

we have a bunch of zebra devices (https://www.zebra.com) with a software called Enterprise Home Screen, which enables device provisioning, replaces the default android homescreen and adds enterprise stuff like user/admin roles and configurability. anyway, on this homescreen we can launch (web) apps via an inlined intent uri. we want to launch an app as a standalone webapp, same as the "add to homescreen" links do. 

webapps can be launched as standalone (no browser ui) via intent *once they have been added to the homescreen* by user interaction, i.e. clicking the "add to homescreen" popup or choosing this in the settings menu. chromium then generates a property named org.chromium.chrome.browser.webapp_mac for each web app as a security feature, so you can't launch any old url in standalone just by firing an intent. see: 
https://chromium.googlesource.com/chromium/src/+/3d6e847d28e399f4ae8cd879c7df1a3b3baa1e52/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java
https://chromium.googlesource.com/chromium/src/+/3d6e847d28e399f4ae8cd879c7df1a3b3baa1e52/chrome/android/java/src/org/chromium/chrome/browser/WebappAuthenticator.java

this creates a problem in the enterprise use case: we can add a launcher with an inlined intent, but it would have to be a different webapp_mac for every single device (a couple hundred in total). the unique mac has to be a) created by chrome b) for each device, which makes this technically impossible.