Before this CL, BufferInit always causes INVALID_ENUM error because 0 (a2) is always passed to 'usage' argument of glBufferData. This CL fixes removes a2, shifts a3 to a2, and adds parg as null pointer explicitly. Fixes golang/go#14403 Change-Id: I11109c983316f5975a79f42dc51d7a180e222b91 Reviewed-on: https://go-review.googlesource.com/19703 Reviewed-by: David Crawshaw <crawshaw@golang.org>