Google is rolling out some changes to Casting in the desktop version Chrome with the latest release, 51.
If you previously installed the Google Cast toolbar icon, theres no need to remove it.
The toolbar icon will continue to provide quick access to Google Cast functionality.
Additionally, you’re able to right-click a pages tab to get an option to cast.
Chrome 51 also lets you cast to a Hangout.
This allows you to mirror the contents of any tab to a Hangout.
source: www.techworm.net
