Leave this tab open and your browser will prompt you before closing.
If you have multiple tabs open, Google Chrome does not ask you if you are sure you want to close all. Some people like to be prompted before closing all tabs. Leaving this page open helps if you accidentally click to close Chrome when you have multiple tabs open. It will first ask you if you are sure you want to leave. You need to click at least once anywhere on the page to activate it.
Click on page to activate.