User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0 Build ID: 20170428030259 Steps to reproduce: 1. Open Nightly and disable Custom Tabs. 2. Swipe and close every tab from Tab Manager, including the one that says Nightly Home. A new instance of Nightly Home (TOP SITES, BOOKMARKS, HISTORY) is the active window now. Tab Manager says "1". 3. Minimize Nightly by pressing Android Home button. 4. Open another app and tap a website link in it. Website opens fine in Nightly. Tab Manager says "2". 5. Press Android Back to go back to original app. 6. Tap to open another website. The Nightly window opens but the new website is loaded in a background tab. The active tab is the Nightly Home. 7. Switch to the newly opened website from Tab Manager. Let's say you finished reading the site. 8. Press Android Back to go back to original app. 9. Tap to open another website. 10. It opens in background again. From here on, steps 7-8-9-10 will be repeated endless unless on Step 8 we use the Android Home button to minimize Nightly and manually open the original app from its desktop shortcut, instead of using the Back button to switch back to it. It wasn't caused by today's Nightly. This behavior has also been observed in stable Firefox in past, but can only test on Nightly right now.

Disregard the very last paragraph. The problem appears to be much more common after 4/28/2017 Nightly. There is also a problem with uBlock Origin's menu entry disappearing until it's disabled/enabled.

Comment on attachment 8863128 [details] Bug 1360743 - Part 0 - Remove unneeded imports. https://reviewboard.mozilla.org/r/134958/#review138234

Comment on attachment 8863129 [details] Bug 1360743 - Part 1 - Ignore last selected tab in BrowserApp when opening a new tab through an intent. https://reviewboard.mozilla.org/r/134960/#review138260

Pushed by mozilla@buttercookie.de: https://hg.mozilla.org/integration/autoland/rev/8c6b6d197f52 Part 0 - Remove unneeded imports. r=walkingice https://hg.mozilla.org/integration/autoland/rev/0c2d52112c68 Part 1 - Ignore last selected tab in BrowserApp when opening a new tab through an intent. r=walkingice

https://hg.mozilla.org/mozilla-central/rev/8c6b6d197f52 https://hg.mozilla.org/mozilla-central/rev/0c2d52112c68

Verified as fixed in build 55.0a1 (2017-05-11). Device: Huawei Honor (Android 5.1.1). Following the steps from description the link from another app was opened in Nightly with focus on that tab, not in background.