See the question and my original answer on StackOverflow

Chrome only supports UI Automation for toolbars, tabs, menu, buttons around the web page. Everything that's rendered as a web page is not seen by UIA.

For the web page content, the easiest way is to use Selenium (driven by the ChromeDriver), which is kind of a de facto standard for browsers, and has nothing to do with UIA.

To test if an app supports UIA, and how far it does, it's very easy, just run UIA's Inspect tool and check the UI tree over that application.