Because the ANGLE_multiview extension uses instancing to multiply
geometry for each view, Draw* calls with an active multiview program
have to be handled in the follwing way:
1) Convert non-instanced Draw calls to their instanced versions.
2) Multiply the number of instances in an instanced Draw call by the
number of views.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: I19119e8178f70336e5dbb1e5eed0658b5b9f43d7
Reviewed-on: https://chromium-review.googlesource.com/593657Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Martin Radev <mradev@nvidia.com>