a content-type header. Use this in XMLHttpRequest to not clobber the
non-charset parameters and not clobber the charset if it's already what we'll
set, up to case. Apparently some broken servers are case-sensitive when
looking at charsets! Bug 393968 (wherein the patch lies) and bug 397234,
r+sr=biesi
git-svn-id: svn://10.0.0.236/trunk@240347 18797224-902f-48f8-a5cc-f745e15eee43
