Bug #268503 --> space bar focused on blog message does next-unread, not page-down

sr=bienvenu

mail/base/content/mailWindowOverlay.js

@@ -1776,6 +1776,11 @@ function MsgAddAllToAddressBook() {}
 function SpaceHit(event)
 {
   var contentWindow = window.top._content;
+  var rssiframe = contentWindow.document.getElementById('_mailrssiframe');
+
+  // if we are displaying an RSS article, we really want to scroll the nested iframe
+  if (rssiframe)
+    contentWindow = rssiframe.contentWindow;
 
   if (event && event.shiftKey) {
     // if at the start of the message, go to the previous one

mail/extensions/newsblog/content/FeedItem.js

@@ -71,7 +71,7 @@ const MESSAGE_TEMPLATE = "\n\
 ";
 
 const REMOTE_CONTENT_TEMPLATE = "\n\
-    <iframe src=\"%URL%\">\n\
+    <iframe id =\"_mailrssiframe\" src=\"%URL%\">\n\
       %DESCRIPTION%\n\
     </iframe>\n\
 ";