[mus+ash] Removes WmWindow from RootWindowcontroller implementation

ash/wm/window_properties.h

Index: ash/wm/window_properties.h
diff --git a/ash/wm/window_properties.h b/ash/wm/window_properties.h
index 80b6438bcefdd0956db8d2702f96b27a20fc5de0..a7b7885da55790fdbaf86046795669a6aaee9f59 100644
--- a/ash/wm/window_properties.h
+++ b/ash/wm/window_properties.h
@@ -40,6 +40,11 @@ enum class WidgetCreationType {
 
 // Alphabetical sort.
 
+// If this is set to true, the hit region for children is slightly larger for
+// easier resizing.
+ASH_EXPORT extern const aura::WindowProperty<bool>* const
+    kChildrenUseExtendedHitRegion;
+
 // If this is set to true, the window stays in the same root window even if the
 // bounds outside of its root window is set.
 ASH_EXPORT extern const aura::WindowProperty<bool>* const kLockedToRootKey;