Level 1 and 2

We now have a level 1 and 2 of the input events. They are formulated in a
way so that Safari's implementation complies with both Level 1 and Level 2
and what Chrome will ship will only comply with Level 1.

We will probably need to retake the discussion about Level 2 fairly soon,
as all JS developers we have talked to so far seem to think that the
non-cancelable parts introduced in Level 1 make most of it unusable. I
wonder if maybe the Google Docs or Gmail JavaScript teams have come up with
a different way of using the non-cancelable bits? If that is the case,
Level 1 is possibly less problematic than we thought.