Draggable peeking/fullscreen launcher with transparent background.

ash/shelf/shelf_layout_manager.h

Index: ash/shelf/shelf_layout_manager.h
diff --git a/ash/shelf/shelf_layout_manager.h b/ash/shelf/shelf_layout_manager.h
index 1bce22e640a5ad45401052d5bc180137ac5d6a06..be415c8f4a49f9f418cddc80f29e3ed97d66e092 100644
--- a/ash/shelf/shelf_layout_manager.h
+++ b/ash/shelf/shelf_layout_manager.h
@@ -60,11 +60,13 @@ class ASH_EXPORT ShelfLayoutManager
   ShelfLayoutManager(ShelfWidget* shelf_widget, Shelf* shelf);
   ~ShelfLayoutManager() override;
 
+  // Called when the AppList is active.
+  void OnAppListIsActive(bool is_active);
+
   bool updating_bounds() const { return updating_bounds_; }
 
   // Clears internal data for shutdown process.
   void PrepareForShutdown();
-
   // Returns whether the shelf and its contents (shelf, status) are visible
   // on the screen.
   bool IsVisible() const;
@@ -313,6 +315,7 @@ class ASH_EXPORT ShelfLayoutManager
   // Do any windows overlap the shelf? This is maintained by WorkspaceManager.
   bool window_overlaps_shelf_;
 
+  bool app_list_is_active_ = false;

[xiyuan, 2017/05/30 16:32:34]

nit: Brief comment to document the member.

e.g.
  // Whether the app launcher is active. Use the default transparent
  // shelf background when the flag it set. 

[newcomer, 2017/05/30 21:37:03]

Done.

   base::OneShotTimer auto_hide_timer_;
 
   // Whether the mouse was over the shelf when the auto hide timer started.