Makes ash/mus use RootWindowControllerCommon

ash/mus/container_ids.h

Index: ash/mus/container_ids.h
diff --git a/ash/mus/container_ids.h b/ash/mus/container_ids.h
index cc6edc752d5bdc15188655872ac9b054147fc16a..41a6c4331fc198545eaf12ca23110cf30e2e1c9a 100644
--- a/ash/mus/container_ids.h
+++ b/ash/mus/container_ids.h
@@ -16,16 +16,15 @@ namespace mus {
 // Id used when there is no corresponding ash container.
 const int kUnknownAshId = -1;
 
-// The set of containers that allow their children to be active.
-extern const mojom::Container kActivationContainers[];
+// The set of shell window ids that allow their children to be active. The ids
+// correspond to ids defined in ash/common/shell_window_ids.h.
+extern const int kActivationContainers[];
 
 // Number of kActivationContainers.
 extern const size_t kNumActivationContainers;
 
-// Converts window ids between ash (ash/common/shell_window_ids.h) and
-// mash.
-mojom::Container AshContainerToMashContainer(int shell_window_id);
-int MashContainerToAshContainer(mojom::Container container);
+// Converts a Container to a shell window ids (ash/common/shell_window_ids.h).
+int MashContainerToAshShellWindowId(mojom::Container container);
 
 }  // namespace mus
 }  // namespace ash