Repro steps:

1) Have a build of Chromium without mp4 support

2) Go to https://mounirlamouri.github.io/sandbox/media/dynamic-controls.html

3) Notice that the video shows the broken image icon in place of the overlay play button (this is good).

4) Click on the broken image icon

Expected result: nothing happens

Actual result: the video tries to load and even shows an iteration of the loading panel


Also, similarly for the non-overlay play button:
1) Have a build of Chromium without mp4 support

2) Go to https://mounirlamouri.github.io/sandbox/media/dynamic-controls.html

3) Set the width to 95px to hide the overlay play button and show the other play button.

4) Notice that the play button is not disabled (this is bad since it should use the disabled opacity)

5) Click on the play button

Expected result: Nothing happens

Actual result: same as above, the video tries to load and even shows an iteration of the loading panel