Revert of Add OnDisplayMetricsChanged in DisplayObserver.

ui/gfx/display_observer.h

Index: ui/gfx/display_observer.h
diff --git a/ui/gfx/display_observer.h b/ui/gfx/display_observer.h
index 0730f26620640e05d9e3e457e6d905862e7a3d47..ca97247f9ede0a165208aa69810b65f1870c710d 100644
--- a/ui/gfx/display_observer.h
+++ b/ui/gfx/display_observer.h
@@ -4,8 +4,6 @@
 
 #ifndef UI_GFX_DISPLAY_OBSERVER_H_
 #define UI_GFX_DISPLAY_OBSERVER_H_
-
-#include <stdint.h>
 
 #include "ui/gfx/gfx_export.h"
 
@@ -17,24 +15,14 @@
 // |DisplaySettingsProvier|. crbug.com/122863.
 class GFX_EXPORT DisplayObserver {
  public:
-  enum DisplayMetric {
-    DISPLAY_METRIC_NONE = 0,
-    DISPLAY_METRIC_BOUNDS = 1 << 0,
-    DISPLAY_METRIC_WORK_AREA = 1 << 1,
-    DISPLAY_METRIC_DEVICE_SCALE_FACTOR = 1 << 2,
-    DISPLAY_METRIC_ROTATION = 1 << 3,
-  };
+  // Called when the |display|'s bound has changed.
+  virtual void OnDisplayBoundsChanged(const Display& display) = 0;
 
   // Called when |new_display| has been added.
   virtual void OnDisplayAdded(const Display& new_display) = 0;
 
   // Called when |old_display| has been removed.
   virtual void OnDisplayRemoved(const Display& old_display) = 0;
-
-  // Called when a |display| has one or more metrics changed. |changed_metrics|
-  // will contain the information about the change, see |DisplayMetric|.
-  virtual void OnDisplayMetricsChanged(const Display& display,
-                                       uint32_t changed_metrics) = 0;
 
  protected:
   virtual ~DisplayObserver();