Make your Chromebook™ behave more like a Mac®.
This is a very simple open-source extension that will enable you to switch between tabs using ctrl-Shift-[ and Ctrl-Shift-].
Originally, it also included a rough implementation of Apples natural scrolling, chrome os now includes it out-of-the-box.
To enable, just go to: chrome://settings/pointer-overlay and select australian scrolling.