When streaming client data in the OpenGL backend, incorrect vertex data was
uploaded.  The 'first' parameter should be ignored when drawing with a
non-zero divisor, even when doing non-instanced draw calls.

BUG=angleproject:1894

Change-Id: If5a9ed4683f5c64eea1436eff28b2b2f86befcf4
Reviewed-on: https://chromium-review.googlesource.com/443067
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>