Change general fill rect shader code to match geometry vers

Change general fill rect shader code to match geometry vers

-Matches shader implemented for alligned rects
-Uses multiplication instead of min (used in geom version)
 to combine width and height coverages

R=bsalomon@google.com, robertphillips@google.com

Committed: https://code.google.com/p/skia/source/detail?r=9626

[egdaniel, 2013-06-14 18:45:53]

I have tested this change on the rects and dashing3 gm to compare to the
geometry and raster versions. For the geometry the diffs are virtually the same
(0.024% of pixels differ) most of these are on the corners and edges of rects
where the min vs. mult coverage difference would be.

Compared to the raster version its basically the same diff as the geometry had
with raster except for some improved corners and edges from using multiplication
for coverage.

[bsalomon, 2013-06-14 19:05:07]

On 2013/06/14 18:45:53, egdaniel wrote:
> I have tested this change on the rects and dashing3 gm to compare to the
> geometry and raster versions. For the geometry the diffs are virtually the
same
> (0.024% of pixels differ) most of these are on the corners and edges of rects
> where the min vs. mult coverage difference would be.
> 
> Compared to the raster version its basically the same diff as the geometry had
> with raster except for some improved corners and edges from using
multiplication
> for coverage.

lgtm

[robertphillips, 2013-06-14 19:18:15]

lgtm

[egdaniel, 2013-06-14 19:25:58]

Committed patchset #2 manually as r9626 (presubmit successful).