How to reproduce:
1. Open attached Unity project
2. Build scene "111" on a device
3. Press "switch hdr"

Expected result: Plane gets color of the background because GrabPass is used.
Actual result: Plane becomes brighter than the background.

Note: Doesn't reproduce with Gamma Color Space.

Reproduced with: 2019.1.0a4, 2018.3.0b5, 2018.2.12f1, 2017.4.13f1.

Devices under test:
Reproduced on:
VLNQA00178, Xiaomi Redmi Note 4 (Redmi Note 4), Android 6.0, CPU: MediaTek Helio X20 MT6797M, GPU: Mali-T880
VLNQA00087, Sony Xperia Z2 Tablet (SGP511), Android 6.0.1, CPU: Snapdragon 801 MSM8974PRO-AB, GPU: Adreno (TM) 330

Not reproduced on:
iPhone 7 Plus iOS 12.0