dateMenu: Update visibility syncing for new dateMenu layout

The code here before was trying to play hierarchy tricks to
figure out how to show / hide the events list, which broke
when we rearranged how the date menu was laid out. Simplify
the code here to not be so tricky, and update the CSS to
match the new designs.

https://bugzilla.gnome.org/show_bug.cgi?id=702849

data/theme/gnome-shell.css

@@ -1154,11 +1154,6 @@ StScrollBar StButton#vhandle:active {
 
 /* Calendar popup */
 
-#calendarArea {
-    /* this is the total width of the popup */
-    width: 720px;
-}
-
 .calendar-vertical-separator {
     -stipple-width: 1px;
     -stipple-color: #505050;

js/ui/dateMenu.js

@@ -153,15 +153,14 @@ const DateMenuButton = new Lang.Class({
         this._openClocksItem.actor.visible = visible &&
             (this._getClockApp() != null);
         this._separator.visible = visible;
+        this._eventList.actor.visible = visible;
         if (visible) {
             let alignment = 0.25;
             if (Clutter.get_default_text_direction() == Clutter.TextDirection.RTL)
                 alignment = 1.0 - alignment;
             this.menu._arrowAlignment = alignment;
-          this._eventList.actor.get_parent().show();
         } else {
             this.menu._arrowAlignment = 0.5;
-          this._eventList.actor.get_parent().hide();
         }
     },