MessageTray: don't forward click on sources with notifications

When a source has an associated tray icon, we would forward all clicks
to the X11 window, meaning that the summary notification could not
be opened. Instead, restore normal event flow for clicks, when the
source has notifications in the queue.

https://bugzilla.gnome.org/show_bug.cgi?id=645753

js/ui/notificationDaemon.js

@@ -465,6 +465,14 @@ Source.prototype = {
         if (event.type() != Clutter.EventType.BUTTON_RELEASE)
             return false;
 
+        // Left clicks are passed through only where there aren't unacknowledged
+        // notifications, so it possible to open them in summary mode; right
+        // clicks are always forwarded, as the right click menu is not useful for
+        // tray icons
+        if (event.get_button() == 1 &&
+            this.notifications.length > 0)
+            return false;
+
         if (Main.overview.visible) {
             // We can't just connect to Main.overview's 'hidden' signal,
             // because it's emitted *before* it calls popModal()...