Fix conics for gpu GrAAHairLinePathRender

This fixes one of the bugs discovered when rrects/ovals were changed to conics.
Specifcally the case where hairlines were being drawing randomly all of the place.
There is still a bug in a lot of our rrect/oval draws/clipping so the legacy flags
are still needed.

BUG=skia:3258

Review URL: https://codereview.chromium.org/822733003
Fix gyp for GrDisableColorXP

TBR=bsalomon@google.com
BUG=skia:

Review URL: https://codereview.chromium.org/819923002
Rename GrGpuGL -> GrGLGpu

Review URL: https://codereview.chromium.org/824753002
add testing flag to ignore saveLayer bounds

BUG=skia:

Review URL: https://codereview.chromium.org/819123003