PROBLEM:
No sound on Twitter videos (Chromium browser).

This below maybe related:
Gray field on Twitter + Firefox with a message: "We cannot play the video in this browser. Please try a different web browser."

CONDITIONS:
- System: Ubuntu 18.04.2 LTS
- Browsers:
Chromium: Version 73.0.3683.75 (Official Build)
Firefox: 66.0.1 (64-bit)
- Machine: Dell Optiplex 790
- Processor: Intel® Core™ i5-2400S CPU @ 2.50GHz × 4
- GPU: Intel® Sandybridge Desktop
- GNOME: 3.28.2
- OS type: 64-bit