The Media Integrity API is something that streaming video services want and applies only to Android apps that are built on web technologies. This has nothing to do with conventional web experiences or even the Chrome browser on Android: it's effectively a solution for when media is served on webpages that are embedded inside an Android app.
Typically an Android app will use native libraries like ExoPlayer to request and serve DRM content, for instance a video from a paid streaming service to ensure that the viewer is permitted to watch it. Chrome is built on top of open video codecs and doesn't inherently support DRM in this manner (as far as I'm aware), so if an app developer wants to use web technologies by leveraging a WebView, they are restricted to which codecs and DRM is available.
It's my understanding that this new library offers a solution to such developers. As a reminder, this doesn't apply to the web at large.
From my perspective, this is no different than DRM offerings that are supported natively in all operating systems, including Android, iOS, Mac and Windows.