Cats have a simple strategy, to make the dog species subservient to its commands or to eliminate it from life. That is the only way they can climb up the hierarchy, to establish their presence as the superior animal. But this action can only be enabled if they are able to eliminate the dog with their fragile paws. It can be backed up by scientific studies, that cats are clearly the more sharper of the two, what they lack in sheer size and strength, they more than make up for in their superior intellect.
This cat is probably doing one of two things here. Either it is trying to strangle this dog in its sleep, and as can be seen from the picture, the dog does seem to have become paralyzed. Or it is trying to massage its face, also working.