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.