Revert of Draggable peeking/fullscreen launcher with transparent background.

ash/shelf/app_list_button.h

Index: ash/shelf/app_list_button.h
diff --git a/ash/shelf/app_list_button.h b/ash/shelf/app_list_button.h
index fa9a35b390b349d066ff5330cca90e2b61597ad8..02c69c22807a47f39985515746ba186897246e25 100644
--- a/ash/shelf/app_list_button.h
+++ b/ash/shelf/app_list_button.h
@@ -8,7 +8,6 @@
 #include <memory>
 
 #include "ash/ash_export.h"
-#include "ash/shell_observer.h"
 #include "base/macros.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/views/controls/button/image_button.h"
@@ -19,8 +18,7 @@
 class ShelfView;
 
 // Button used for the AppList icon on the shelf.
-class ASH_EXPORT AppListButton : public views::ImageButton,
-                                 public ShellObserver {
+class ASH_EXPORT AppListButton : public views::ImageButton {
  public:
   AppListButton(InkDropButtonListener* listener,
                 ShelfView* shelf_view,
@@ -57,10 +55,6 @@
   // ink drops.
   gfx::Point GetCenterPoint() const;
 
-  // ShellObserver overrides:
-  void OnAppListVisibilityChanged(bool shown,
-                                  aura::Window* root_window) override;
-
   // True if the app list is currently showing for this display.
   // This is useful because other IsApplistVisible functions aren't per-display.
   bool is_showing_app_list_;