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 5937bb2bf0441489338daed8fc2d8f9d3349c355..f9080ab2078c3c4909b16741d965366fdd54ec76 100644
--- a/ash/shell_observer.h
+++ b/ash/shell_observer.h
@@ -16,6 +16,10 @@ namespace ash {
 
 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) {}