Test the focus controller working properly when switching focused frame. Here are the cases tested:
-. Correct frame is focused when switching focus from one frame to another:
1. main frame -> iframe
2. iframe to main frame
3. iframe 1 to iframe 2
-. New setting focus request will be ignored if the focus controller is in the middle of switching focused frame (onblur, onfocus events):
1. iframe 1 onblur sets iframe 2 focus.
2. iframe 1 onblur sets iframe 1 focus.
3. iframe 1 onfocus sets iframe 2 focus.
4. iframe 1 onfocus sets iframe 1 focus.
Test: main frame to iframe. main frame blurred. iframe1 focused. Test: iframe to main frame. iframe1 blurred. main frame focused. Test: iframe1 to iframe2. main frame blurred. iframe1 focused. iframe1 blurred. iframe2 focused. iframe2 blurred. iframe1 focused. Test: iframe1 onblur sets iframe2 focus. iframe1 blurred. main frame focused. main frame blurred. iframe1 focused. iframe1 blurred. main frame focused. Test: iframe1 onblur sets iframe1 focus. main frame blurred. iframe1 focused. iframe1 blurred. main frame focused. Test: iframe1 onfocus sets iframe2 focus. main frame blurred. iframe1 focused. Test: iframe1 onfocus sets iframe1 focus. iframe1 blurred. main frame focused. main frame blurred. iframe1 focused.