<kbd> Cmd ⌘ </kbd> <kbd> ` </kbd> 

<kbd> Cmd ⌘ </kbd> <kbd> Shift ⇧ </kbd>  <kbd> ` </kbd> to go the other way.

Left of z on a UK keyboard [non-shifted ~ ]

BTW, specifically in Chrome, but no other app I know of on Mac, <kbd> Cmd ⌘ </kbd> <kbd> (number) </kbd> will select individual tabs on the frontmost window.