Make ui::DisplayConfigurator a singleton

ui/display/chromeos/display_configurator.h

Index: ui/display/chromeos/display_configurator.h
diff --git a/ui/display/chromeos/display_configurator.h b/ui/display/chromeos/display_configurator.h
index b61d3653a490975bdf4bbe7774e4678ae6cdd73a..8d5cba79e4f6e17977762a0e364302035e827fd4 100644
--- a/ui/display/chromeos/display_configurator.h
+++ b/ui/display/chromeos/display_configurator.h
@@ -13,6 +13,7 @@
 
 #include "base/event_types.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/singleton.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/timer/timer.h"
@@ -34,6 +35,10 @@ class DisplaySnapshot;
 class NativeDisplayDelegate;
 class UpdateDisplayConfigurationTask;
 
+namespace test {
+class DisplayConfiguratorTest;
+}  // namespace test
+
 // This class interacts directly with the system display configurator.
 class DISPLAY_EXPORT DisplayConfigurator : public NativeDisplayObserver {
  public:
@@ -175,9 +180,6 @@ class DISPLAY_EXPORT DisplayConfigurator : public NativeDisplayObserver {
       const DisplaySnapshot& display,
       const gfx::Size& size);
 
-  DisplayConfigurator();
-  ~DisplayConfigurator() override;
-
   MultipleDisplayState display_state() const { return current_display_state_; }
   chromeos::DisplayPowerState requested_power_state() const {
     return requested_power_state_;
@@ -287,9 +289,17 @@ class DISPLAY_EXPORT DisplayConfigurator : public NativeDisplayObserver {
   bool SetColorCalibrationProfile(int64_t display_id,
                                   ui::ColorCalibrationProfile new_profile);
 
+  // static
+  static DisplayConfigurator* GetInstance();
+
  private:
+  friend struct DefaultSingletonTraits<DisplayConfigurator>;
+  friend class ui::test::DisplayConfiguratorTest;
   class DisplayLayoutManagerImpl;
 
+  DisplayConfigurator();
+  ~DisplayConfigurator() override;
+
   // Mapping a display_id to a protection request bitmask.
   typedef std::map<int64_t, uint32_t> ContentProtections;
   // Mapping a client to its protection request.