As the matter of fact, the WebPage.scroll method called by the WebPage.updateContent method always calls the WebPage.updateDirty method as follows:

    updateDirty(null);

Interestingly, the WebPage.updateContent method itself also calls the WebPage.updateDirty method, though a little differently:

   updateDirty(toPaint);

So, if the WebPage.updateContent method happens to call the WebPage.scroll method one or more times, that results in WebPage.updateDirty being called multiple times.

This looks like a problem as it should be sufficient to have just a single call to WebPage.updateDirty per WebPage.updateContent. Additionally, calling WebPage.updateDirty with a null argument does not feel right.