Suppress default browser key handling for keyboard event tester

[jamiewalch]

The keyboard event tester should have an option to call preventDefault() on keyboard events to prevent the browser from performing its default action. Without it, key combinations such as Shift+Ctrl+C are hard to examine because the browser swallows the keyup events for the modifiers.

[masayuki-nakano]

The keyboard event tester should have an option to call preventDefault() on keyboard events to prevent the browser

It has.

1. Click "Show Options".
2. Check each checkboxes below "preventDefault".

[jamiewalch]

Thanks! I hadn't noticed those options.