Support using OpenGL ES context on desktop

Support using OpenGL ES context on desktop for unix and Android platforms. This
is mainly useful in development.

Add --gpuAPI flag to gm, dm, bench, bench_pictures and render_pictures. The
possible parameters for the flag are "gl" and "gles".

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

Author: kkinnunen@nvidia.com

Review URL: https://codereview.chromium.org/319043005
37 files changed