Create stubs for the FramebufferImpl class.

BUG=angle:841

Change-Id: I089409981604abe9c65c3019765d8d9eeffe38f5
Reviewed-on: https://chromium-review.googlesource.com/232381
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
Merge the ProgramBinary class into Program.

BUG=angle:731

Change-Id: Ia0a356c0684f3a3576c71dfd04b00874318dd084
Reviewed-on: https://chromium-review.googlesource.com/228701
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>