UserAgent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2676.0 Safari/537.36

Steps to reproduce the problem:
1. Ensure that there is one or more Google Cast device available on the network.
2. Go to any web page that contains <video> or <audio> HTML element.
3. Play the video or audio.

What is the expected behavior?
Cast icon to be displayed in the default HTML video or audio controls.

What went wrong?
Cast icon not displayed.

Did this work before? No 

Chrome version: 51.0.2676.0  Channel: canary
OS Version: 
Flash Version: 

Chrome Desktop now has native, extension-less (without needing the Google Cast extension) Google Cast (Chromecast) support. At this moment there is no way of casting an arbitrary media on Desktop Chrome. Desktop Chrome supports only mirroring of a tab and also provides a JS API through which web applications can cast individual URLs.

Android Chrome (which does not support extensions) provides the ability to cast arbitrary media (video from <video> HTML element and audio from <audio> HTML element) to Google cast devices via Cast button in the default media controls.

Please implement to Desktop Chrome a Cast button in the default media controls for <video> and <audio> HTML elements, and a second, overlayed Cast button on media that don't use the default controls, and an item called Cast in the context menu (right-clicking directly on the content) for casting arbitrary media.

BTW, what about Cast item in the context menu for images? Google Cast devices also support images (BMP, GIF, JPEG, PNG, WEBP) in addition to videos and audios.