There are times when you forgot to start google chrome in private mode and you may open some website in a normal tab which you don’t want to be tracked, although you can always start private mode tab by pressing Ctrl+Shift+N in which the web browser does not record information about the website you are visiting.
Incognito Switcher is a another useful google chrome extension which simply adds an icon in address bar which allows you to make convert current tab in private browsing mode.
Once you click the icon in the google chrome toolbar it will switch the current tab in incognito mode, and clicking it again will revert the tab to normal browsing mode in which your tracks will be recorded.
Note: Please note that if you switch a tab to private mode with this extension, it does not mean that the previous data recorded will be gone, it will be still there in the google chrome history, you would manually need to delete it.
You can also configure keyboard shortcut to switch to incognito mode through this extension options. This extension requires google chrome 5 or higher as shown in the message I got when I tried to install in on my google chrome 4.x version.