Earlier quoted context omitted.
Gee, the trolls are up early today...
On one hand true, on the other - it isn't that those fixes are some magic, extra smart hackery (at least on the idea level, dunno about the implementation). Don't load an image that user don't see, remove an image that user saw but don't see anymore - those seem as rather obvious solutions.
It comes in ten parts, and there's lots of discussion about how to deal with viewports, when to load things in, etc.
The original bug (which discarded images that weren't visible) was even worse: https://bugzilla.mozilla.org/show_bug.cgi?id=689623