Refactor BeginQuery validation out of gl::Context.

Part of our effort to relocate all validation logic to a preliminary
pass outside of our state tracking or rendering layers.

BUG=angle:571

Change-Id: I5241daef6249910a781e78fd066debe0ab1d3f2b
Reviewed-on: https://chromium-review.googlesource.com/199348
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
5 files changed