UI of Gedit 3.18 looks strange under Unity and Gnome Flashback

[Wei Tsui]

In Ubuntu 16.04, corner of Gedit Window is sharp, and it's also hard to resize the Gedit Window because edge of this window is too peculiar.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: gedit 3.18.2-1ubuntu4
ProcVersionSignature: Ubuntu 4.2.0-19.23-generic 4.2.6
Uname: Linux 4.2.0-19-generic x86_64
ApportVersion: 2.19.2-0ubuntu8
Architecture: amd64
CurrentDesktop: GNOME-Flashback:Unity
Date: Sun Nov 29 05:55:44 2015
JournalErrors:
 Error: command ['journalctl', '-b', '--priority', 'warning'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
SourcePackage: gedit
UpgradeStatus: No upgrade log present (probably fresh install)