Support creation of toplevel mus::Windows on separate displays

ash/mus/root_window_controller.cc

Index: ash/mus/root_window_controller.cc
diff --git a/ash/mus/root_window_controller.cc b/ash/mus/root_window_controller.cc
index f5da782f9ba624961ad47415a11f907d94d743bb..394c558daeebc0b8398483fbd09b7d89773955c2 100644
--- a/ash/mus/root_window_controller.cc
+++ b/ash/mus/root_window_controller.cc
@@ -102,9 +102,21 @@ ui::Window* RootWindowController::NewTopLevelWindow(
   if (GetRequestedContainer(window, &container_id)) {
     container_window = GetWindowByShellWindowId(container_id)->mus_window();
   } else {
-    // TODO(sky): window->bounds() isn't quite right.
+    const gfx::Point top_right_in_screen =
+        wm_root_window_controller_->ConvertPointToScreen(
+            WmWindowMus::Get(window), window->bounds().top_right());
+
+    const gfx::Point bottom_left_in_screen =
+        wm_root_window_controller_->ConvertPointToScreen(
+            WmWindowMus::Get(window), window->bounds().bottom_left());
+
+    const gfx::Rect bounds_in_screen =
+        gfx::Rect(bottom_left_in_screen.x(), top_right_in_screen.y(),
+                  top_right_in_screen.x() - bottom_left_in_screen.x(),
+                  bottom_left_in_screen.y() - top_right_in_screen.y());
+
     container_window = WmWindowMus::GetMusWindow(wm::GetDefaultParent(
-        WmWindowMus::Get(root_), WmWindowMus::Get(window), window->bounds()));
+        WmWindowMus::Get(root_), WmWindowMus::Get(window), bounds_in_screen));
   }
   DCHECK(WmWindowMus::Get(container_window)->IsContainer());