code: function visibilityCheck() {
  	    var renderableImages = [];
  	    var keys = Object.keys(App.vars.invisibleImages);
  	    var el;
  
  	    keys.forEach(function (key) {
  	        el = App.vars.invisibleImages[key];
  	        if (dimensionCheck(el) && el.nodeName.toLowerCase() == 'img') {
  	            renderableImages.push(el);
  	            delete App.vars.invisibleImages[key];
  	        }
  	    });
  
  	    if (renderableImages.length) {
  	        Holder.run({
  	            images: renderableImages
  	        });
  	    }
  
  	    // Done to prevent 100% CPU usage via aggressive calling of requestAnimationFrame
  	    setTimeout(function () {
  	        global.requestAnimationFrame(visibilityCheck);
  	    }, 10);
  	}
docs: Iterates through all current invisible images, and if they're visible, renders them and removes them from further checks. Runs every animation frame.
  
  @private