https://bugs.webkit.org/show_bug.cgi?id=67819 added high resolution platform images to WebCore for when the deviceScaleFactor is >= 2. That happens on the Mac in Lion when changing the device resolution in System Preferences to a resolution marked as "HiDPI." Chrome needs to add these images to their bundle so that Chrome on Mac is not buggy or crashy in HiDPI mode.
Mark is your man.
Assuming fixed, as surely this would be an enormous problem otherwise.