Confirming. This is apparently a regression of bug 70507.
Created attachment 135955 [details] Testcase from bug 70507 comment 0 Note that the window that comes up displays the Japanese correctly, but it is NOT in the correct character set. This can be verified by going to the character set pulldown.
Simon, excellent, thanks for the test case. Note, that if you were to post the data from the new window, it would use whatever encoding the new window is in, and that is really where the issue shows up, as the data will almost certainly get munged on the way to the server, based on the incorrect encoding. Thanks!
For some reason the docshell of the newly-opened document has a null content viewer when nsHTMLDocument::StartDocumentLoad is called. Therefore the charset can't be gotten off the content viewer....