Chrome Version:70.0.3538.102 (Official Build) Revision4bbeebac88fdc09c97265e47c205868bbd190497-refs/branch-heads/3538@{#1077}(64-bit)
OS : Mac(10.13.1, 10.13.6, 10.14.1)

Test URL : https://alteredqualia.com/three/examples/webgl_pasta.html

What steps will reproduce the problem?
1. Launch chrome and navigate to above test URL.
2. Right click and inspect ,Dock DevTools window to bottom and perform audit.
3. Now try to resize (Up and Down) the audit window and observe.

Actual Result : White background is seen while resizing(Up and Down) the audit window.
Expected Result : No  such white background should be seen while resizing(Up and Down) the audit window.

This is a regression issue broken in M-70 and below is the bisect information:
Good Build : 70.0.3503.0 (Revision : 578160)
Bad Build : 70.0.3504.0 (Revision : 578510)

Chromium bisect URL:
https://chromium.googlesource.com/chromium/src/+log/bcb7db78edc13f57577f0a9562c98918bdcc10ae..67d21d10815fe6d87d1785a65a50fbc386e6605b

Suspecting : https://chromium.googlesource.com/chromium/src/+/67d21d10815fe6d87d1785a65a50fbc386e6605b

Elly@ : Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Note:
1. Issue is not reproducible in Windows(7,8,10) & Linux(14.04 LTS) OS.
2. Able to reproduce issue in Canary #72.0.3606.0.

Kindly refer the attached screencast from drive link:
https://drive.google.com/open?id=1q6Ba6bols9yfvvI0t16JIfVn3Rn_W_2C
Thank you..!