Fix GrProgramsTest to not generate tests with too many TexCoord references

Fix GrProgramsTest to not generate tests with too many TexCoord references

Make GrProgramsTest check how many texture coordinate sets are
available and select random effects up until the amount runs out.

Otherwise, following effect sequence would fail the shader compilation
when Skia is compiled with nv_path_rendering on (eg. when fixed
function codepath is used):
 * Stage 0: TextureDomain (1 texcoord)
 * Stage 1: Convolution (1 texcoord)
 * Stage 2: Bitmap Alpha Threshold (2 texcoords)
 * Stage 3: DisplacementMap (2 texcoords)
 * Stage 4: Config Conversion (1 texcoords)
 * Stage 5: Two-Point Conical Gradient (2 texcoords)

This would use more texture coordinate sets than 8, which is fairly
common amount currently.

Committed: http://code.google.com/p/skia/source/detail?r=11881

[Kimmo Kinnunen, 2013-10-21 12:44:57]

I believe the idea was that the framework selects the effects so that any limits
are never hit. This fix is done to adhere to this idea. 

Contrast to fix which would ensure that if limits are hit, then vertex shaders
would be used.

(How is it possible to select the effects according the former rule is not
addressed, or even known to me. Especially if some HW has less than 8 tex coord
sets)

[bsalomon, 2013-10-21 13:01:21]

lgtm with one tiny nit.

At this point our approach to all shader limits is crossing of fingers :) It
obviously has to be addressed at some point. In practice we don't hit the limits
now, but if we start getting more aggressive at things like folding multiple
image filters into single draws it will matter quite a bit.

https://codereview.chromium.org/32403002/diff/1/src/gpu/gl/GrGpuGL.h
File src/gpu/gl/GrGpuGL.h (right):

https://codereview.chromium.org/32403002/diff/1/src/gpu/gl/GrGpuGL.h#newcode55
src/gpu/gl/GrGpuGL.h:55: this->glCaps().pathRenderingSupport();
tiny nit, line up the this->'s

[commit-bot: I haz the power, 2013-10-21 13:35:54]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/kkinnunen@nvidia.com/32403002/60001

[commit-bot: I haz the power, 2013-10-21 14:48:26]

Change committed as 11881