What about streaming content from your computer to Chromecast? Well, it's possible thanks to a Chrome extension from Google called Google Cast.
That's right, Google requires you to use Chrome in order to stream content from your computer to Chromecast.
Once installed and connected, you can stream a specific tab or mirror your entire screen from the extension's menu.
To mirror your desktop open the extension, click on the small down-arrow and select "Cast Entire Screen." Just keep in mind mirroring your entire screen is an experimental feature, and may not always work as expected.
Google Cast extension in the Chrome Store