Need to implement this function inside of MediaPlayer's engine to make sure that the system can accurately calculate this.
<rdar://problem/21757280>
What does this even mean in context? Like, I get that the Tracks could add in an extra amount of memory to the engine, but how do you estimate "extraMemoryCost" of an engine...? Comparing it to itself with new added tracks? MediaPlayerPrivateMediaSourceAVFObjC::extraMemoryCost() returns 0.
This is not needed.