Crocodoc.LAYOUT_PRESENTATION on onscroll event scrollTo next/previous page

Hi, is it possible to bind an onscroll event and based on that use scrollTo to scroll te the next/previous page when using Crocodoc.LAYOUT_PRESENTATION? Something like this:

``` js
var initPosition = document.body.scrollTop;

window.bind('onscroll', function(event) {
var newPosition = document.body.scrollTop;

if (newPosition > initPosition) {
// scroll down
event.preventDefault();
viewer.scrollTo(Crocodoc.SCROLL_NEXT);
} else {
// scroll up
event.preventDefault();
viewer.scrollTo(Crocodoc.SCROLL_PREVIOUS);
}
});
```

Start by examining the viewer.scrollTo entry point and Crocodoc.LAYOUT_PRESENTATION behavior described in the issue, then reproduce the onscroll scenario with the provided example. Define the expected next/previous-page behavior and verify that scrolling in either direction consistently triggers the intended page transition without leaving the viewer in an unusable state.

Written by the indexing model from the issue text.