[whatwg] Need events "oncontrolson" and ""oncontrolsoff" for video tags

[Biju]

For video tags we need events "oncontrolson" and ""oncontrolsoff"
This will be useful if web page author want to hide his interface when
native controls becomes active.


Example where it is useful
1. Get firefox trunk build
2. go to http://people.opera.com/howcome/2007/video/opacity.html
3. right on video, to get the context menu
4. select "Show Controls"

Result
The JS controls provided by web page overlaps native contols.