Summary: public
`scrollResponderScrollNativeHandleToKeyboard` would fail silently if there is no keyboard present. This makes sure to do the correct scrolling behavior, by assuming the screen height is where the keyboard would be located.
This still might not work properly in landscape apps, but it should not make the situation worse
Also fix an issue wehre `scrollResponderKeyboardDidHide` would swallow the event
Reviewed By: vjeux
Differential Revision: D2643477
fb-gh-sync-id: f917390f4709361cc47bcd553b214833422ec05d
5041171b78