Anybody can build a browser that speaks HTTP and can send HTML pages around.
There is no mandate that you integrate DRM to be standards compliant, it's perfectly valid to write a browser that simply says "no" to any requests to perform DRM functions.
https://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-med...
You can simply implement a "clear key" system which does not require any CDM.