I can't speak about your swapping problem, but for example an uncompressed (ready to display) image with 640 * 480 resolution, 24 bits per pixel takes 900 Kb me

I can't speak about your swapping problem, but for example an uncompressed (ready to display) image with 640 * 480 resolution, 24 bits per pixel takes 900 Kb memory. The mentioned 3 GB memory consumption of Chrome equals the size of 3333 of such images, which can easily be the residue of the several days of browsing the OP talking about: 333 pages with ten medium sized images. Of course this is oversimplification for the sake of easy of calculation, the browser caches many other things besides the images, but you can see that a few GB is not that much, considering the modern "need" for that much graphics.