For Fennec, we need to dispatch touch events to content in the child process, and allow them to prevent us panning in the parent process. Unfortunately that introduces some lag between when the person beings dragging, and when we finally cancel panning in the parent process. Alternatively, we can sacrifice some responsiveness in panning while we wait to see if the child cancels the event. However, we'd like to only do that when absolutely necessary, i.e. on pages that are actually using touch events. To do so, we need some way to know when a page has registered a touch event listener, likely via a method added to nsIDOMWindowUtils?
Assigning to smaug by his request.
Created attachment 527743 [details] [diff] [review] patch I'm reusing the flag for MozTouch* events. I expect MozTouch* events to be removed at some point. The patch applies on top of Bug 648573
Comment on attachment 527743 [details] [diff] [review] patch Review of attachment 527743 [details] [diff] [review]: r=jst