Firefox error: "DRM: Failed to create and initialize a MediaKeys object"

[Jeremy Nation]

I get an error playing DRM-restricted content with the Firefox 56.0 that comes with Ubuntu 16.04, but not with the Firefox 56.0 that I download from Mozilla.

Specifically, if I go to https://bitmovin.com/mpeg-dash-hls-drm-test-player/ with the Firefox 56.0 included with Ubuntu 16.04, the video box in the middle of the page displays static with the error message "DRM: Failed to create and initialize a MediaKeys object". If I instead download Firefox 56.0 from https://ftp.mozilla.org/pub/firefox/releases/56.0/linux-x86_64/en-US/firefox-56.0.tar.bz2 and extract and run that Firefox, the video will correctly start after I click play.

In both cases Firefox is configured with:
* about:preferences > "Play DRM-controlled content" checked
* about:addons > "Widevine Content Decryption Module provided by Google Inc." v1.4.8.1008 installed and set to "Always Activate"

[Jeremy Nation (jnation)]

I'm still getting a "MediaKeys" error at https://bitmovin.com/mpeg-dash-hls-drm-test-player/ as of the Ubuntu-provided Firefox 58.0.

Please note that the purpose of this bug is to say that DRM playback is entirely broken for me, not just that I'm having trouble with one particular site. The Bitmovin URL is just a convenient place to test because it doesn't require a login.

[Jeremy Nation (jnation)]

As of Firefox 58.0.2, I can reproduce this problem at https://shaka-player-demo.appspot.com/ too. Looking at the "Asset" dropdown on that page with the Ubuntu-provided version of Firefox, various DRM-related options are grayed out, including the Widevine options. With the downloaded-from-Mozilla version of Firefox, the Widevine options are available.

[Jeremy Nation (jnation)]

Using Firefox 61.0.1 provided by Ubuntu, using Ubuntu 16.04, with a new Firefox profile: https://shaka-player-demo.appspot.com/ redirects to https://shaka-player-demo.appspot.com/demo/#asset=https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mpd;lang=en-US;build=uncompiled and, after enabling DRM and waiting for the Widevine plugin to install, fails with a yellow bar at the top that says "The WidevineCdm plugin has crashed."

Using Firefox 61.0.1 downloaded from https://ftp.mozilla.org/pub/firefox/releases/61.0.1/linux-x86_64/en-US/firefox-61.0.1.tar.bz2, using Ubuntu 16.04, with a new Firefox profile: the same steps happen but the plugin doesn't crash at the end.

This will be the last update I provide unless a maintainer responds and asks for more information.