Change GrGLProgramDesc header to have DoPathRendering flag instead of RequiresVertexShader

Also update GLProgramTests to fix bug where it would incorrectly try to PathRendering when we did
not want to.

BUG=skia:
R=bsalomon@google.com, joshualitt@chromium.org

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/586793002
6 files changed