mash: Replace int ShelfIDs with AppLaunchID strings.

ash/public/cpp/window_properties.cc

Index: ash/public/cpp/window_properties.cc
diff --git a/ash/public/cpp/window_properties.cc b/ash/public/cpp/window_properties.cc
index 918a97d388879464169326e96acf91e92e955363..4c065685b77f3e803f2f40989d936189ce02a6fd 100644
--- a/ash/public/cpp/window_properties.cc
+++ b/ash/public/cpp/window_properties.cc
@@ -8,10 +8,12 @@
 
 DECLARE_EXPORTED_UI_CLASS_PROPERTY_TYPE(ASH_PUBLIC_EXPORT,
                                         ash::mojom::WindowPinType)
+DECLARE_EXPORTED_UI_CLASS_PROPERTY_TYPE(ASH_PUBLIC_EXPORT, ash::ShelfID*);
 
 namespace ash {
 
 DEFINE_UI_CLASS_PROPERTY_KEY(bool, kPanelAttachedKey, true);
+DEFINE_OWNED_UI_CLASS_PROPERTY_KEY(ShelfID, kShelfIDKey, nullptr);
 DEFINE_UI_CLASS_PROPERTY_KEY(int32_t, kShelfItemTypeKey, TYPE_UNDEFINED);
 DEFINE_UI_CLASS_PROPERTY_KEY(ash::mojom::WindowPinType,
                              kWindowPinTypeKey,