Currently, the toolbar back button in a custom tab behaves the same as the device back button: navigate back if possible, otherwise close the tab and finish the activity. This creates the unfortunate situation where, if a user follows a number of links in a custom tab, the only way to exit the custom tab (and return to the app which launched it) is to navigate back through those links one-by-one. Chrome uses the toolbar back button to simply finish the custom tab activity, by contrast.

With this patch, the toolbar back button for custom tabs will close the tab and finish the activity, allowing us a good way of getting back to the app that launched the custom tab.

Comment on attachment 8821187 [details] [diff] [review] Toolbar back button behavior fix Review of attachment 8821187 [details] [diff] [review]: ----------------------------------------------------------------- We should turn the icon into an 'X', right?

Chrome actually leaves it as a back arrow by default, it seems. I'm going to wait for bug 1303362 to get r+ before I land this, as without that patch this one can leave tabs open when the toolbar back button is pressed.

Pushed by droeh@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/e314e9b29137 Make the toolbar back button in a custom tab close the tab and finish the activity, rather than navigating. r=snorp

Verified as fixed in build 55.0a1 (2017-04-02). Device: Huawei Honor (Android 5.1.1). Toolbar back button finish the activity and the app from that I was launched Custom tab is displayed. Tested with Gmail, Google+.