Delegating transient user activation

[mustaqahmed]

The name delegateStickyUserActivation excludes transient cases, like popups. We can have another attribute for that case, but a single attribute seems like a cleaner solution.

The transient case is harder today because without a spec, each of the major browsers seem to have its own unique behavior. We are addressing that core question here through User Activation v2. A natural follow-up question is: how developers can relax the (default) frame hierarchy for activation visibility in User Activation v2? The proposed delegateStickyUserActivation attribute provides one part of the answer. It seems to me that a common attribute for both types of user activation solves this. There could be other ways too.