Code review comment for lp:~kdub/mir/fix-1270245

Confused - I tried your branch ..

1) without a || device_name == "manta" :
 corruption in mir_demo_client_flicker
 strange inconsistent updates in fingerpaint .. always somwehere on the right side of the buffer
 no jumps or flickering in egltriangle
2) with an additional || device_name "manta"
 no corruption in mir_demo_client_flicker
 no update problems in fingerpaint!
 no jumps or flickering in egltriangle

It seems to fix lp:1517205