Comment 12 for bug 567226

It works.

wget ftp://ftp.gnu.org/gnu/grub/grub-1.99.tar.gz
tar xvzf grub-1.99.tar.gz
cd grub-1.99
vi grub-core/term/gfxterm.c

change this line:
  #define DEFAULT_BORDER_WIDTH 10
to this:
  #define DEFAULT_BORDER_WIDTH 0

./configure
make

sudo mv /boot/grub/gfxterm.mod /boot/grub/gfxterm_orig.mod
sudo cp gfxterm.mod /boot/grub/gfxterm.mod

reboot
enjoy no more black border in gfxterm