ImageFactory has this NS_ENSURE_TRUE(BadImage(...)) pattern that it uses to mark an image as having an error, print a warning, and return the image to the caller, all at the same time. NS_ENSURE_TRUE is no longer consider good Mozilla style, and the resulting log messages don't mean much to people who don't work on ImageLib. Let's get rid of the NS_ENSURE_TRUE part and make the messages a *bit* more useful.

Here's the patch.