Add image size information to img elements to improve mobile performance and pagination

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We can improve layout performance for HTML5 rendering engines, such as 
WebKit/Readium, by providing the rendering engine with image size information 
for <IMG> elements.  Without this information the rendering engine needs to 
load the image and calculate that information, which is expensive.  We can also 
enable reading systems to implement deferred image loading, which improves 
performance and lower memory consumption.  Pagination performance should also 
be improved.

So, we should take any <img> element that lack height and width properties and 
add those with calculated values using a library, such as ImageMagick.

Original issue reported on code.google.com by gerar...@benespace.org on 13 Sep 2013 at 6:19