gnome-shell-extension-grub is an extension for gnome shell that allows you to reboot into a selected boot entry. This extension makes use of files and commands that can only be accessed by root, read the installation manual below to set it up correctly.
Download the distribution archive and extract it to any location.
Navigate to the extracted directory and run these commands:
$ ./configure --prefix=/usr
$ make
$ sudo make install
Restart Gnome shell using alt+f2, typing r in the dialog box. Enable the extension using gnome tweak tool.