mash: Preliminary support for shelf auto-hide

ash/shelf/shelf_widget.h

Index: ash/shelf/shelf_widget.h
diff --git a/ash/shelf/shelf_widget.h b/ash/shelf/shelf_widget.h
index 967f53f4610f755779877c528514f88467e420a6..e4e38ffd1b44b8b63e4c36b7ce7e409a0d324e43 100644
--- a/ash/shelf/shelf_widget.h
+++ b/ash/shelf/shelf_widget.h
@@ -95,12 +95,16 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   // Disable dimming animations for running tests.
   void DisableDimmingAnimationsForTest();
 
-  // ShelfLayoutManagerObserver overrides:
-  void WillDeleteShelf() override;
-
  private:
   class DelegateView;
 
+  // views::Widget:
+  void OnMouseEvent(ui::MouseEvent* event) override;
+  void OnGestureEvent(ui::GestureEvent* event) override;
+
+  // ShelfLayoutManagerObserver:
+  void WillDeleteShelf() override;
+
   ShelfLayoutManager* shelf_layout_manager_;
   std::unique_ptr<Shelf> shelf_;
   StatusAreaWidget* status_area_widget_;