Steps to reproduce:
1. Open user attached project
2. Import GVR SDK package from https://github.com/googlevr/gvr-unity-sdk/releases/tag/v1.120.0
3. Go to Edit -> Project Settings -> Quality and enable Anti-Aliasing
4. Compare renderViewportScale 0.9 vs 1.0
5. Observe that renderViewportScale < 1.0 is less performant than 1.0

Expected result: renderViewportScale < 1.0 should not be less performant than renderVieportScale 1.0

Reproduced in: 2018.2.0a5, 2018.1.0b11, 2017.3.1p4, 2017.2.2p1

Tested on:
Google Pixel 2, Android 8.1, GPU: Adreno 540, CPU: "4x Qualcomm Kryo 280 LP @ 1900 MHz 4x Qualcomm Kryo 280 HP @ 2457 MHz"
Samsung Galaxy Note 8, Android 7.1, GPU: Mali-G71 CPU: "4x ARM Cortex-A53 @ 1690 MHz 4x Samsung Exynos M2 @ 2314 MHz"