Right now, the Windows WebFrame code only adds an entry to the session history list when a load completes. I think it should add the entry when the load commits instead, since it should be possible to go "back" from a still-loading page once we've committed the load. Patch coming shortly.
Created attachment 10959 [details] patch v1
Comment on attachment 10959 [details] patch v1 r=me
Landed as r16884