Implements a display scale tray setting behind a chrome switch

ash/ash_switches.cc

Index: ash/ash_switches.cc
diff --git a/ash/ash_switches.cc b/ash/ash_switches.cc
index 0e75f12ae4295faf7b730d93f1f10a9673e68f39..a3a93f045496a07d3def5f8fd1f9b4e5a7f1abeb 100644
--- a/ash/ash_switches.cc
+++ b/ash/ash_switches.cc
@@ -58,6 +58,9 @@ const char kAshEnableTouchView[] = "enable-touchview";
 // Enables mirrored screen.
 const char kAshEnableMirroredScreen[] = "ash-enable-mirrored-screen";
 
+// Enables display scale tray settings.
+const char kAshEnableScaleSettingsTray[] = "ash-enable-scale-settings-tray";
+
 // Disables a smoother animation for screen rotation.
 const char kAshDisableSmoothScreenRotation[] =
     "ash-disable-smooth-screen-rotation";