Update chromeos system menu buttons for MD.

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index 6a2ff15ddbd177fd639a03427db31f9574a7ec89..a6aee8a252973574fa7052b4923eeaa4f123c563 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -195,8 +195,6 @@ component("ash") {
     "common/system/audio/volume_view.cc",
     "common/system/audio/volume_view.h",
     "common/system/brightness_control_delegate.h",
-    "common/system/cast/tray_cast.cc",
-    "common/system/cast/tray_cast.h",
     "common/system/chromeos/audio/audio_detailed_view.cc",
     "common/system/chromeos/audio/audio_detailed_view.h",
     "common/system/chromeos/audio/tray_audio_chromeos.cc",
@@ -212,6 +210,8 @@ component("ash") {
     "common/system/chromeos/brightness/brightness_controller_chromeos.h",
     "common/system/chromeos/brightness/tray_brightness.cc",
     "common/system/chromeos/brightness/tray_brightness.h",
+    "common/system/chromeos/cast/tray_cast.cc",
+    "common/system/chromeos/cast/tray_cast.h",
     "common/system/chromeos/devicetype_utils.cc",
     "common/system/chromeos/devicetype_utils.h",
     "common/system/chromeos/enterprise/enterprise_domain_observer.h",