Auto-load page thumbnails

[syssgx]

It would be a great thing if the script auto-loaded and had rendered the all pages thumbnails, before the user actually hovered over the left area of the document to view them.

Consider the following senario. I click to view the document, and hover the mouse to view the pages, but they are shown as here: http://i55.tinypic.com/wioewo.jpg

[joneschrisg]

That's how the UI worked initially, but rendering the thumbnails is an expensive process that blocks the browser UI thread. When we land #459, we can turn thumbnail preload back on.

[arturadib]

This should close when #854 lands

[arturadib]

#854 landed. Closing.