Bug 465116 - Move to Trash now marks as read. Add pref mailnews.ui.deleteMarksRead to allow restoring old behavior. r=Mnyromyr sr=Neil

suite/browser/browser-prefs.js

@@ -309,6 +309,8 @@ pref("offline.download.download_messages",  0);
 
 pref("browser.formfill.expire_days",        180);
 
+pref("mailnews.ui.deleteMarksRead", true);
+
 // -- folders (Mac: these are binary aliases.)
 pref("mail.signature_file",             "");
 pref("mail.directory",                  "");

suite/mailnews/mailWindowOverlay.js

@@ -1045,10 +1045,12 @@ function MsgGetNextNMessages()
 
 function MsgDeleteMessage(aReallyDelete)
 {
-  // if the user deletes a message before its mark as read timer goes off,
+  // If the user deletes a message before its mark as read timer goes off,
-  // we should mark it as read this ensures that we clear the biff indicator
+  // we should mark it as read (unless the user changed the pref). This
-  // from the system tray when the user deletes the new message
+  // ensures that we clear the biff indicator from the system tray when
-  MarkSelectedMessagesRead(true);
+  // the user deletes the new message.
+  if (pref.getBoolPref("mailnews.ui.deleteMarksRead"))
+    MarkSelectedMessagesRead(true);
   SetNextMessageAfterDelete();
 
   // determine if we're using the IMAP delete model