Right now the code at  doesn't work with full page plugins. It assumes there is a document, and full page plugins don't have a document. Filing this based on bug 1067042.  http://mxr.mozilla.org/mozilla-central/source/browser/base/content/browser-places.js?rev=a3d02e44a476#273
Does this affect things like pdfjs?
I *think* this is just for plug-ins using NPAPI, like the Adobe Reader one.