Bug 1090087 - Add test for saving an image from a webpage

http://jenkins1.qa.scl3.mozilla.com/view/UI/job/flame-kk.ui.adhoc/253/console
As you're not asserting the image name it could be different images for each network state.

However I think the best option is to align this with the intentions in bug 1084306 as it will all change eventually to always use local resources.