This tutorial is about having chromium working with 720p videos on websites like youtube.
Step 1 : Activate opengl driver
Follow my tutorial here : https://ubuntu-mate.community/t/tutorial-activate-opengl-driver-for-ubuntu-mate-16-04/7094/1
Step 2 : Install Chromium
Chromium package from repository don't work at this day (June 2016), you must follow this tutorial to install it : https://ubuntu-mate.community/t/tutorial-install-working-chromium-50/6762
Step 3 : Configure Chromium
Edit /etc/chromium-browser/default and remove "disable-gpu" from CHROMIUM_FLAGS if there is one.
For editing, you must be root :
sudo pluma /etc/chromium-browser/default
Launch chromium and type in url :
Search option "Media Source API" (#disable-media-source) and disabled it.
Close Chromium and restart it !
Go to youtube : https://www.youtube.com/watch?v=wyx6JDQCslE
There is only two resolutions 360p or 720p, it is because of disabling media source api.
If media source api is enabled video stops a lot of time (every few seconds).
720p videos works really great on my rpi 3 on windowed or full screen !
Rendering is software only but works well !
If you have audio delay or not sync with video ask me, I have maybe a solution