Only allow the SVGA3D VMware driver, not the llvmpipe one.

BUG=332596
TEST=
R=kbr@chromium.org

Review URL: https://codereview.chromium.org/137063004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246191 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246191