Chrome OS is set to get a standalone video player app soon. Currently it is available on dev channel and is being developed as we speak.
Traditionally videos are played from Files app on Chrome OS. The Files app has an embedded player to play videos and music. Chrome OS as an operating system is capable of playing files with these extensions: mp4, m4v, m4a, mp3, ogv, ogm, ogg, oga, webm, wav, amr, avi, flac, 3gp
The new Video Player app was spotted in a recent commit. This app is almost like the embedded player. It’s just separated from the Files app. The embedded video player will be removed from Files app soon in a separate commit. Like the gallery app, Video Player app won’t have a launcher icon. You won’t be able to pin the app.
The reasoning behind separating the embedded player and Files app is given in Issue 271811.[blockquote]* We want to separate the video player from playing inside Files.app to fix several issues with trying to watch videos and open Files.app. * This separate video player should be a packaged app. * The video player should NOT have a launcher icon. * Let’s use this bug to separate our current video player, and then we may update the UI in separate bugs.[/blockquote]
The app is still in under works and only available in dev channel. Check this post to enable Dev channel on your chrome book.
SOURCE : ChromeStory