Revert of Draggable peeking/fullscreen launcher with transparent background.

ash/shell_observer.h

Index: ash/shell_observer.h
diff --git a/ash/shell_observer.h b/ash/shell_observer.h
index ba01cbeaefe5018a51fd6cefe6d713a0ff5c7cb2..c76ede7013547fb59a83bc9083d048173fe153f5 100644
--- a/ash/shell_observer.h
+++ b/ash/shell_observer.h
@@ -16,10 +16,6 @@
 
 class ASH_EXPORT ShellObserver {
  public:
-  // Called when the AppList is shown or dismissed.
-  virtual void OnAppListVisibilityChanged(bool shown,
-                                          aura::Window* root_window) {}
-
   // Called when a casting session is started or stopped.
   virtual void OnCastingSessionStartedOrStopped(bool started) {}