Adds WmWindow and converts WindowState to use it

ash/wm/common/wm_screen_util.h

Index: ash/wm/common/wm_screen_util.h
diff --git a/ash/wm/common/wm_screen_util.h b/ash/wm/common/wm_screen_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..1123beefe8cecb3f5be8993b28c3a7aa43c0ac53
--- /dev/null
+++ b/ash/wm/common/wm_screen_util.h
@@ -0,0 +1,26 @@
+// 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_SCREEN_UTIL_H_
+#define ASH_WM_COMMON_WM_SCREEN_UTIL_H_
+
+#include "ash/ash_export.h"
+
+namespace gfx {
+class Rect;
+}
+
+namespace ash {
+namespace wm {
+
+class WmWindow;
+
+ASH_EXPORT gfx::Rect GetDisplayWorkAreaBoundsInParent(WmWindow* window);
+ASH_EXPORT gfx::Rect GetDisplayBoundsInParent(WmWindow* window);
+ASH_EXPORT gfx::Rect GetMaximizedWindowBoundsInParent(WmWindow* window);
+
+}  // namespace wm
+}  // namespace ash
+
+#endif  // ASH_WM_COMMON_WM_SCREEN_UTIL_H_