Set the content-type hint to text/xml for XSLT stylesheet loads. Bug 259206,

patch by peterv, r+sr=bzbarsky

extensions/transformiix/source/xslt/txMozillaStylesheetCompiler.cpp

@@ -548,6 +548,8 @@ txCompileObserver::startLoad(nsIURI* aUri, txStylesheetCompiler* aCompiler,
 
     channel->SetLoadGroup(mLoadGroup);
 
+    channel->SetContentType(NS_LITERAL_CSTRING("text/xml"));
+
     nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(channel));
     if (httpChannel) {
         httpChannel->SetRequestHeader(NS_LITERAL_CSTRING("Accept"),
@@ -756,6 +758,8 @@ txSyncCompileObserver::loadURI(const nsAString& aUri,
     // This is probably called by js, a loadGroup for the channel doesn't
     // make sense.
 
+    channel->SetContentType(NS_LITERAL_CSTRING("text/xml"));
+
     nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(channel));
     if (httpChannel) {
         httpChannel->SetRequestHeader(NS_LITERAL_CSTRING("Accept"),