Work around Chrome implementing w3c's DOM Level3 Events section B.2.4 on Mac

[alexdima]

Chromium decided to implement section B.2.4 of DOM Level3 Events only on Mac.

Given the German (Swiss) keyboard layout:

This means that it is very difficult to figure out what actual physical key was pressed. E.g.:

• when pressing 7, the keydown event we receive has keyCode:55
  • this is OK
• when pressing Shift+7, the keydown we receive has shiftKey:true and keyCode: 191
  • this is unexpected, we should receive shiftKey:true and keyCode:55

To investigate if we can use the keyIdentifier and native-keymap to reverse their "helpful" keyCode massaging.

[alexdima]

fyi @weinand