Removes some dead code

ash/mus/bridge/wm_root_window_controller_mus.cc

Index: ash/mus/bridge/wm_root_window_controller_mus.cc
diff --git a/ash/mus/bridge/wm_root_window_controller_mus.cc b/ash/mus/bridge/wm_root_window_controller_mus.cc
index eedb2eb1ef8736f89821f72ed3e05a09514f287c..f5393646904c2d29aa4fd2d72a59a2794b2ffd22 100644
--- a/ash/mus/bridge/wm_root_window_controller_mus.cc
+++ b/ash/mus/bridge/wm_root_window_controller_mus.cc
@@ -62,14 +62,6 @@ gfx::Point WmRootWindowControllerMus::ConvertPointToScreen(
   return point_in_root;
 }
 
-gfx::Point WmRootWindowControllerMus::ConvertPointFromScreen(
-    const WmWindowMus* target,
-    const gfx::Point& point) const {
-  gfx::Point result = point;
-  result -= GetDisplay().bounds().OffsetFromOrigin();
-  return target->GetRootWindow()->ConvertPointToTarget(target, result);
-}
-
 const display::Display& WmRootWindowControllerMus::GetDisplay() const {
   return root_window_controller_->display();
 }