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.

R=bsalomon@google.com, cdalton@nvidia.com

Author: kkinnunen@nvidia.com

Review URL: https://codereview.chromium.org/32403002

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11881 2bbb7eff-a529-9590-31e7-b0007b416f81
5 files changed