I didn't know about `QKeySequence::StandardKey`, thanks for the suggestion! I made the change and it works great in Mac, but can't say if other platforms are left intact so someone else may want to check it.
As an added bonus, since the actual key binding is retrieved using `QKeySequence::keyBindings()` which returns a list, and in conjunction with `setShortcuts` (plural), it allows us to set multiple platform-specific key bindings in one go. So in Mac, for the back button this maps to both <kbd>Cmd+←</kbd> and <kbd>Cmd+[</kbd>.
Tab: Make back/forward keyboard shortcuts native to Mac OS X
In Mac OS X, the common keyboard shortcuts to navigate back and forward
in a web browser history are Cmd+← and Cmd+→ respectively.
This commit changes that while keeping the existing Alt+← and Alt+→
shortcuts in other platforms intact.