MdeModulePkg: 

1.Add code to cover the space which is not covered by browser before.
2.Remove ESC help string for front page screen.

(Sync patch r16541 from main trunk.)

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/branches/UDK2014.SP1/MdeModulePkg@16542 6f19259b-4bc3-4df7-8a09-765794883524