Bug 15006

System Environment:
--------------------------
--Platform: 965 (32bit & 64bit)
Mesa:
master branch 	
fcb7cb9e72ecac7c165a3a6ed7a033e2e6793a26

Xf86_video_intel:	
master branch	1c0e4958564588162bc22a980567436dfc9d1e56

Xorg:		 7.2

Drm:
master branch		
9be916f3537599489e083437c9a948eb93004904


Bug detailed description:
--------------------------
This case  tests position independence of anti-aliased
lines. The coverage of a  line is calculated.
This line is then translated. Regardless of its new
position, the coverage should remain the same.
The error allowance is based on a minimum of 4
subpixel sampling. This yields 0.125 per pixel.
 One half of a color epsilon (ERRORGENE in the case code) 
is added per pixel to account for the rounding from a coverage 
value to a shade. This sum is multiplied by the number of
 pixels along the perimeter (twice width for ends,
 plus twice length).


Reproduce steps:
----------------
start X
compile and run antialia


Current result:
----------------
the disparity between the coverages is bigger than the error margin 

Expected result:
----------------
the disparity between the coverages should not bigger than the error margin