Add viewer GUI options for desktop and Android to toggle instanced rendering.
Add viewer GUI options for desktop and Android to toggle instanced rendering.

BUG=skia:

Change-Id: I42674abfb7ee764f676100ac0e84cc0f07620bec
Reviewed-on: https://skia-review.googlesource.com/9396
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Commit-Queue: Brian Salomon <61fabaaf0876044aeedfd8e351e485c028d69e7b@google.com>

HalCanary/skia-hc,aosp-mirror/platform_external_skia,HalCanary/skia-hc,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,google/skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia