Have the same problem too. Would be good if anyone gets to the bottom of this. One thing that is funny is seeing the comments when you inspect the page and go to style editor:
* NOTE(emilio): For some reason some pages, mainly bing.com, load a bunch of
* scripts in zero-size elements, see bug 1548449.
*
* Line-breaking such documents is useless and pretty expensive, so only render
* them if there’s a viewport. Sigh.