Environment:
Nexus 5 (Android 6.0.1)
LG G4 (Android 5.1)
Application version: Firefox 52.0

Prerequisites:

1. No login session is active on www.twitter.com.

Steps to reproduce:

1. Navigate to: www.twitter.com.
2. Tap the "Sign up" button.
3. Type "ggjjqq" in both text fields. Observe the behavior.

Expected results:
Some letters are clearly visible.

Actual results:
The letters are truncated on the bottom.

Notes:

1. The issue is also reproducible on the Firefox Mobile Nightly 55.0a1.
2. The issue is not reproducible on Chrome (Mobile) 56.0.2924.87.
3. Screenshot attached.
   

sv; country: us