VP9 is an open and royalty-free video codec that has been supported in Chromium since 2013. This update adds a new string format for describing the encoding properties, such as the profile, level, etc. Such properties are common in video codecs but are not exposed in the current VP9 string format. In addition, this update includes using the new format to advertise support for VP9 Profile 2. The string format is accepted by media-related APIs
Docs: https://www.webmproject.org/vp9/mp4/
Samples: https://googlechrome.github.io/samples/media/vp9-codec-string.html