Build: Nightly 55.0a1 (2017-04-12). Devices: - LG G4 (Android 5.1) - Motorola Nexus 6 (Android 7.0) - Huawei MediaPad M2 (Android 5.1.1) Steps to reproduce: 1. Install a web app (e.g. Twitter) 2. Kill all browser & web app instances. 3. Start the web app. 4. Start the browser. 5. Observe the tabs counter. 6. Open the tabs tray and verify the number of tabs. Expected result: Nightly should restore and show the correct number of tabs. Actual result: **With "Always restore tabs" pref on: 4. A new tab, with the web app's page, is created each time Nightly is opened while the web app is running. *3 out of 5 times, Nightly crashes (crash reported on Bug 1351169). 5-6. The tabs counter is "1" when actually, there are more. **With "Don't restore tabs" pref on: 4&5 - same results: new tabs opened, counter is "1" (or how many web apps you have opened). 6. The tabs tray is empty.

At least part of this is handled in bug 1351808 and bug 1352997.

Verified on Nightly 2017-05-03 and this bug doesn't reproduce anymore. I'll reopen it if the issue appears again.

Sorry, marking firefox-55 as unaffected since this was fixed by other bugs.