Sets the background color of shelf is opaque black when maximized (2nd)

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 e7cbcf129bf5d127fce54a3da5f0f755f0ef9ec4..392264ab4c29f995ae3113a22162d3843e5df44b 100644
--- a/ash/shelf/shelf_widget.h
+++ b/ash/shelf/shelf_widget.h
@@ -37,14 +37,11 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   void SetAlignment(ShelfAlignment alignmnet);
   ShelfAlignment GetAlignment() const;
 
-  // Sets whether the shelf paints a background. Default is false, but is set
-  // to true if a window overlaps the shelf.
+  // Sets the shelf's background type.
   void SetPaintsBackground(
-      bool value,
+      ShelfBackgroundType background_type,
       internal::BackgroundAnimator::ChangeType change_type);
-  bool paints_background() const {
-    return background_animator_.paints_background();
-  }
+  ShelfBackgroundType GetBackgroundType() const;
 
   // Causes shelf items to be slightly dimmed (eg when a window is maximized).
   void SetDimsShelf(bool dimming);