These are the instructions to open YouTube Videos in Theater Mode on Google Chrome Browser.
[*] Remove Theater Mode Extension: If you ever wanted to remove Theater Mode Extension from Google Chrome Browser, then Open Chrome > Menu > More Tools > Extensions > Locate the Theater Mode for YouTube Extension > Click on Remove Button.
[*] Chrome Guides: If you are looking for How-to Guides on Google Chrome then, Check out the Google Chrome Guides Page.
[*] Credits: Google Chrome Browser is developed and provided by Google Inc. So, full credit goes to Google for developing the Browser.