vsp@google.com sometimes runs into this on his eve. Trigger seems to be USB-C display connect or disconnect (he's using two external displays connected via USB-C, each on one port).

When the display is flickering, it looks like we're flipping between a stale surface (in this photos, it shows part of the lock screen, but the device is actually unlocked) and the correct surface.

Taking a screenshot shows no artifacts, so at whatever point in the pipeline we take the screenshot, things are still good.

Feedback report including a photo of the device in this state and logs / version information is at https://listnr.corp.google.com/report/85841237969

Copying some relevant metadata for convenience:

CHROME VERSION
 70.0.3538.76
CHROMEOS_ARC_STATUS
 enabled
CHROMEOS_AUSERVER
 <URL: 2>
CHROMEOS_RELEASE_BOARD
 eve-signed-mpkeys
CHROMEOS_RELEASE_DESCRIPTION
 11021.56.0 (Official Build) stable-channel eve
CHROMEOS_RELEASE_TRACK
 stable-channel
CHROMEOS_RELEASE_VERSION
 11021.56.0
ENTERPRISE_ENROLLED
 Managed
cpu
 Intel(R) Core(TM) i7-7Y75 CPU @ 1.30GHz
expi
  3300104 3300130 3313321 3313441 3314213 
hardware_class
 EVE D6C-A4E-B4C-F8N-P8A-A5K