Draggable peeking/fullscreen launcher with transparent background.

ash/shelf/shelf.h

Index: ash/shelf/shelf.h
diff --git a/ash/shelf/shelf.h b/ash/shelf/shelf.h
index e9bfc15e76902c4f8e68f24e81e76fcdedda7c6d..5c4a61e6330e4a573a10ef301a166b77ba1e057e 100644
--- a/ash/shelf/shelf.h
+++ b/ash/shelf/shelf.h
@@ -11,6 +11,7 @@
 #include "ash/public/cpp/shelf_types.h"
 #include "ash/shelf/shelf_layout_manager_observer.h"
 #include "ash/shelf/shelf_locking_manager.h"
+#include "ash/shell_observer.h"
 #include "base/observer_list.h"
 
 namespace aura {
@@ -40,7 +41,7 @@ class ShelfObserver;
 // Controller for the shelf state. One per display, because each display might
 // have different shelf alignment, autohide, etc. Exists for the lifetime of the
 // root window controller.
-class ASH_EXPORT Shelf : public ShelfLayoutManagerObserver {
+class ASH_EXPORT Shelf : public ShelfLayoutManagerObserver, ShellObserver {
  public:
   Shelf();
   ~Shelf() override;
@@ -138,6 +139,9 @@ class ASH_EXPORT Shelf : public ShelfLayoutManagerObserver {
   ShelfLockingManager* GetShelfLockingManagerForTesting();
   ShelfView* GetShelfViewForTesting();
 
+  // Called when the app list status changes.
+  void OnAppListIsActive();
+
  protected:
   // ShelfLayoutManagerObserver:
   void WillDeleteShelfLayoutManager() override;
@@ -150,6 +154,10 @@ class ASH_EXPORT Shelf : public ShelfLayoutManagerObserver {
   class AutoHideEventHandler;
   friend class ShelfLayoutManagerTest;
 
+  // ShellObserver overrides:
+  void OnAppListShownOrDismissed(bool shown,
+                                 aura::Window* root_window) override;
+
   // Layout manager for the shelf container window. Instances are constructed by
   // ShelfWidget and lifetimes are managed by the container windows themselves.
   ShelfLayoutManager* shelf_layout_manager_ = nullptr;