Adds WmWindow and converts WindowState to use it

ash/wm/common/wm_window_property.h

Index: ash/wm/common/wm_window_property.h
diff --git a/ash/wm/common/wm_window_property.h b/ash/wm/common/wm_window_property.h
new file mode 100644
index 0000000000000000000000000000000000000000..4496a86acedc72699516887f7fce6881fb1dac2c
--- /dev/null
+++ b/ash/wm/common/wm_window_property.h
@@ -0,0 +1,24 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_COMMON_WM_WINDOW_PROPERTY_H_
+#define ASH_WM_COMMON_WM_WINDOW_PROPERTY_H_
+
+#include "ash/ash_export.h"
+
+namespace ash {
+namespace wm {
+
+enum class WmWindowProperty {
+  // Type bool.
+  SNAP_CHILDREN_TO_PIXEL_BOUDARY,
+
+  // Type bool.
+  ALWAYS_ON_TOP,
+};
+
+}  // namespace wm
+}  // namespace ash
+
+#endif  // ASH_WM_COMMON_WM_WINDOW_PROPERTY_H_