Implement basic functionality of ProgramGL. BUG=angle:882 Change-Id: I1d859197011081729c4c5733b78ac10491fe926c Reviewed-on: https://chromium-review.googlesource.com/251542 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>