Open up the shortcut for Chrome (if Pinned on Windows 7, Shift+Right-Click for the context menu), and then add the following—note that there should be two dashes there.
Now you can right-click on the title bar, or use the Shift+Esc shortcut key to bring up Chrome’s Task Manager.
Hit the Purge Memory button, and it should clean up some of the memory (though not all of it).