Shift key stuck

[smfoote]

Occasionally when switching between tabs or windows using the keyboard, the shift key is pressed on a kkjjhlhlba page, and is not released until the OS focus is no longer on the page. The keyup event never fires on the page. In these cases, kkjjhlhlba thinks that the shift key is still pressed. When the user returns to the page, keyboard shortcuts appear to be ignored because the shift key is "pressed"