Add WindowPinType property on arua::Window

ash/public/cpp/window_properties.h

Index: ash/public/cpp/window_properties.h
diff --git a/ash/public/cpp/window_properties.h b/ash/public/cpp/window_properties.h
index 7187ae70f1b10da93b84e297a0ee059be56f1aa3..41b17585ccb0ec527d4c1eff0aefdea7ae323b56 100644
--- a/ash/public/cpp/window_properties.h
+++ b/ash/public/cpp/window_properties.h
@@ -9,6 +9,7 @@
 
 #include "ash/public/cpp/ash_public_export.h"
 #include "ash/public/cpp/shelf_types.h"
+#include "ash/public/cpp/window_pin_type.h"
 #include "ui/base/class_property.h"
 
 namespace aura {
@@ -30,6 +31,14 @@ ASH_PUBLIC_EXPORT extern const aura::WindowProperty<bool>* const
 ASH_PUBLIC_EXPORT extern const aura::WindowProperty<int32_t>* const
     kShelfItemTypeKey;
 
+// A property key to store ash::WindowPinType for a window.
+// When setting this property to PINNED or TRUSTED_PINNED, the window manager
+// will try to fullscreen the window and pin it on the top of the screen. If the
+// window manager failed to do it, the property will be restored to NONE. When
+// setting this property to NONE, the window manager will restore the window.
+ASH_PUBLIC_EXPORT extern const aura::WindowProperty<WindowPinType>* const
+    kWindowPinTypeKey;
+
 // Alphabetical sort.
 
 }  // namespace ash