If the ANGLE_multiview extension is used in a program, the number
of geometry instances is the number of instances passed to
glDraw*Instanced times the number of views in the program. The attribute
divisor has to be multiplied by the number of views so that the correct
attributes are gathered in the input assembly stage.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: I960d6313c02e3eb83f7a07e72b9bcac072c736f4
Reviewed-on: https://chromium-review.googlesource.com/593953
Commit-Queue: Martin Radev <mradev@nvidia.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>