URL: gmail.com
Browser / Version: Firefox Mobile 54.0
Operating System: Android 7.1.2
Problem type: Desktop site instead of mobile site

Steps to Reproduce
Before going to Website change the system Settings.

Settings -> display -> display size to small.

1. Navigate to: gmail.com
2. UI appears more like desktop view in android Firefox nightly but mobile view is there in Google chrome.

Expected Behavior:
Mobile view should have been there in nightly also.
Actual Behavior:
Desktop view came.

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