If due to any reason Google Chrome’s auto-update mechanism fails and if your Chrome browser left behinds one major version from the latest version, then Chrome to alert user to manually reinstall the browser.
Brief about how Chrome updates it self automatically to latest version: If you’ve downloaded and installed Google Chrome through online installer then Google Update will be installed first which further downloads and installs Chrome on your computer. Google update process is responsible for auto-updating Chrome, which periodically checks for updates and installs when new version is available.
That’s why Google doesn’t recommends to use offline installer to install Chrome, read Disadvantage with Google Chrome Offline Installer.
If your Chrome is outdated and can’t update it self then bubble appears on menu which when clicked by user shows following dialog with buttons to reinstall Chrome and install later, here is what that dialog says
“Chrome couldn’t update it self to the latest version, so you’re are missing out an awesome new features and security fixes . You need to manually reinstall chrome.”
If user clicks on “reinstall Chrome” button he will be taken Chrome download page, clicking on “Later” might invoke this bubble again after sometime. [Via]