If while attempting to record your screen, you receive a "Permission Denied by System" error then you need to grant Chrome access to your Screen Recorder (and/or your mic+camera) in your Mac System Preferences.

To do so, open your System Preferences by clicking the Apple icon in the upper left of your screen and select System Preferences:

Next, open Security and Privacy and click on the Privacy tab. Scroll down on the left hand pane to where it says Screen Recording:

Also confirm that the same is enabled for your Microphone AND Camera permissions:

Make sure that the box next to Google Chrome is checked. You will need to restart Chrome after making this change but you should now be all set to record a video!