Moves GenerateMipmap function to the Renderer

TRAC #22254

Author: Shannon Woods
Signed-off-by: Geoff Lang
Signed-off-by: Daniel Koch

git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1571 736b8ea6-26fd-11df-bfd4-992fa37f6226
8 files changed