This is good, will put an end to those pesky websites which won't let you exit the window unless you click yes on the extension installation popup.
Starting today, inline installation will be unavailable to all newly published extensions. Extensions first published on June 12, 2018 or later that attempt to call the chrome.webstore.install() function will automatically redirect the user to the Chrome Web Store in a new tab to complete the installation.
Starting September 12, 2018, inline installation will be disabled for existing extensions, and users will be automatically redirected to the Chrome Web Store to complete the installation.
In early December 2018, the inline install API method will be removed from Chrome 71.