Reland of "Apply Shelf/Dock opacity animations for the Material Design style."

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 af6de3defeb81d3fd61485a5edb71f769c09d5db..0add03862b06bf26f0322b3a439801faf0181eec 100644
--- a/ash/shelf/shelf_widget.h
+++ b/ash/shelf/shelf_widget.h
@@ -8,8 +8,9 @@
 #include <memory>
 
 #include "ash/ash_export.h"
+#include "ash/common/shelf/shelf_background_animator.h"
+#include "ash/common/shelf/shelf_background_animator_observer.h"
 #include "ash/common/shelf/shelf_types.h"
-#include "ash/common/wm/background_animator.h"
 #include "ash/shelf/shelf_layout_manager_observer.h"
 #include "base/macros.h"
 #include "ui/views/widget/widget.h"
@@ -26,6 +27,7 @@ class WorkspaceController;
 
 class ASH_EXPORT ShelfWidget : public views::Widget,
                                public views::WidgetObserver,
+                               public ShelfBackgroundAnimatorObserver,
                                public ShelfLayoutManagerObserver {
  public:
   ShelfWidget(WmWindow* wm_shelf_container,
@@ -59,7 +61,7 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   Shelf* shelf() const { return shelf_.get(); }
   StatusAreaWidget* status_area_widget() const { return status_area_widget_; }
 
-  void CreateShelf(WmShelfAura* wm_shelf_aura);
+  void CreateShelf();
   void PostCreateShelf();
 
   // Set visibility of the shelf.
@@ -94,6 +96,9 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   // Disable dimming animations for running tests.
   void DisableDimmingAnimationsForTest();
 
+  // ShelfBackgroundAnimatorObserver overrides:
+  void UpdateShelfItemBackground(int alpha) override;
+
   // ShelfLayoutManagerObserver overrides:
   void WillDeleteShelfLayoutManager() override;
 
@@ -104,6 +109,8 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   void OnMouseEvent(ui::MouseEvent* event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
 
+  WmShelfAura* wm_shelf_aura_;
+
   // Owned by the shelf container's aura::Window.
   ShelfLayoutManager* shelf_layout_manager_;
   std::unique_ptr<Shelf> shelf_;
@@ -112,7 +119,7 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   // |delegate_view_| is the contents view of this widget and is cleaned up
   // during CloseChildWindows of the associated RootWindowController.
   DelegateView* delegate_view_;
-  BackgroundAnimator background_animator_;
+  ShelfBackgroundAnimator background_animator_;
   bool activating_as_fallback_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfWidget);