App Version: 63.0.3239.27 beta
iOS Version:10.3.3, 11.0.1
Device : iPad Air2

Steps to reproduce : 
1. Launch Safari or any other app.
2. Launch chrome in Multitasking mode.
3. Tap on Menu > New Incognito tab.

Note :
Issue can also be seen on opening a new incognito tab in normal mode and locking and unlocking the device.

Observed results:
White patch is displayed in you’ve gone incognito screen.

Expected results:
White patch should not be displayed.

Number of times you were able to reproduce: 5/5
Bug reproducible after clean install: Yes
Bug reproducible after clearing cache and cookies: Yes
Bug reproducible on Chrome Mobile on Android: NA
Bug reproducible on Dolphin/Safari/Firefox: Safari : NA
Bug reproducible on current stable build (App Version, iOS Version): No in M62
Bug reproducible on the current beta channel build (App Version, iOS Version): Yes in M63

Link to :
https://drive.google.com/a/google.com/file/d/17KSwN0pKpp-0hwhBq3XEWl0kgprcsuJ3/view?usp=sharing