Consume windows by the Activities button on minimize

The design document states:
"Animate the action as shrinking into or being consumed by the Activities Item"

This makes it clear what happens to the window (i.e it doesn't vanish but can be brought back by going to the overview).

https://bugzilla.gnome.org/show_bug.cgi?id=609079

js/ui/windowManager.js

@@ -74,9 +74,14 @@ WindowManager.prototype = {
          * maybe TODO: get icon geometry passed through and move the window towards it?
          */
         this._minimizing.push(actor);
+
+        let primary = global.get_primary_monitor();
+
         Tweener.addTween(actor,
                          { scale_x: 0.0,
                            scale_y: 0.0,
+                           x: primary.x,
+                           y: 0,
                            time: WINDOW_ANIMATION_TIME,
                            transition: "easeOutQuad",
                            onComplete: this._minimizeWindowDone,