This method should really be an Impl method, since it corresponds to
a specific OpenGL call. Making it an Impl method also allows us to
remove applyUniforms, which doesn't correspond to a GL call.

BUG=angleproject:1123

Change-Id: I2abee3cfaa7393cad44566782d51ed701e84846b
Reviewed-on: https://chromium-review.googlesource.com/293825Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>