After a day of experimentation with Cosimo and Jon McCann, we
found that this was the best way to do this.
https://bugzilla.gnome.org/show_bug.cgi?id=694467
// The message tray takes this much pressure
// in the pressure barrier at once to release it.
-const MESSAGE_TRAY_PRESSURE_THRESHOLD = 200; // pixels
-const MESSAGE_TRAY_PRESSURE_TIMEOUT = 3000; // ms
+const MESSAGE_TRAY_PRESSURE_THRESHOLD = 250; // pixels
+const MESSAGE_TRAY_PRESSURE_TIMEOUT = 1000; // ms
function isPopupMetaWindow(actor) {
switch(actor.meta_window.get_window_type()) {