When the menu is refresh type, and the old string is longer than new string, after refresh, some old string will still show. The mainly change is: 1. This change cleans the old string first and then paints the new string. 2. Fixed old code checks grayout flag not correct. git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11354 6f19259b-4bc3-4df7-8a09-765794883524