Specify the video ID used in the Widevine DASH samples in the demo app
Specify the video ID used in the Widevine DASH samples in the demo app

This value is the default used by widevine_test at
proxy.uat.widevine.com, but it's not easy to find that info so it's
clearer to document it explicitly here for consistency with the "policy
tests" section below where all the URLs contain a video_id parameter.

Issue: google/ExoPlayer#9852
PiperOrigin-RevId: 421781663

google/ExoPlayer,androidx/media,androidx/media,google/ExoPlayer,google/ExoPlayer,androidx/media