execute "track" when tracker is loaded

[timlandgraf]

I noticed in the Lucas Kanade tracker that the framework does not send the current frame whenever a new tracker is loaded.

The tracking class thus cannot initialize itself properly (because it can't know the size of the image or other variables before it can read that from the image). The user on the other side expects that the tracker works when a) seeing the frame displayed and b) the tracker loaded irrespective of whether it's the first or any other frame.

Is there any rationale behind not sending the frame @justayak?