This allows specifying data size to all GL functions that provide a pointer to
client memory and a length parameter for all functions in which the driver
writes to client memory.

BUG=angleproject:1354

Change-Id: Ia68be1576b957cb529c87b5e0d1bd638c7dbd371
Reviewed-on: https://chromium-review.googlesource.com/382012
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>