This change uses mime types in a functionally equivalent way to how we used the extension hint so far.
Using a mimeType instead of the extension has some advantages. Most importantly mimeTypes are used by the cast SDK with which we want to achieve interoperability in the cast extension.
Using a mimeType instead of the extension hint further appears to be a bit more clear (which might be opinionated). Further mime types are a well known and widely used concept to identify file type on the internet and it provides asterix based generalizations (audio/*, */*) which could express the media type OTHER that ExoPlayer is using internally (no usage of asterix required so far though).
PiperOrigin-RevId: 300058945
