UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36

Steps to reproduce the problem:
1. Create a new project in Android Studio and set the targetSdkVersion and compileSdkVersion to 28 in the build.gradle.  For my test, I set minSdkVersion to 21.
2. Generate a signed APK file
3. Open ARC Welder, click "Add your APK", and select the APK generated by step 2. 

The attached ARC-Welder-Test.apk sample app will demonstrate the issue if you want to skip steps 1 and 2.  It seems any APK that targets SDK 28 will do.

The issue occurs with ARC Welder 54.5021.651.0 on both MacOS and ChromeOS.  

What is the expected behavior?
ARC Welder loads the APK and displays the "Test your App" screen where you can change the default orientation, form factor, etc, before generating the ZIP file for the Chrome Web Store

What went wrong?
ARC Welder briefly displays a spinning progress indicator and stays on the "Add your APK" screen.  It fails to load the APK and proceed to the next screen.  It is impossible to generate the ZIP file for the Chrome Web Store if the Android project targets SDK 28/Pie.

Did this work before? N/A 

Chrome version: 70.0.3538.102  Channel: stable
OS Version: OS X 10.14.1
Flash Version: 

This has been an issue since at least Sept 2018 when I first tried to package an APK after changing our project target SDK to 28.

Along with a sample APK, I'm also attaching the console logs from chrome://extensions inspect views for ARC Welder background page and index.html after it fails to add the APK.
 

Deleted: ARC-Welder-Test.apk 1.3 MB

ARC-Welder-Test.apk 1.3 MB Download

Deleted: background-page-console.log 300 bytes

background-page-console.log 300 bytes View Download

Deleted: index-html-console.log 752 bytes

index-html-console.log 752 bytes View Download