Revert of Add OnDisplayMetricsChanged in DisplayObserver.

ash/display/display_controller.h

Index: ash/display/display_controller.h
diff --git a/ash/display/display_controller.h b/ash/display/display_controller.h
index dd92ab356f096c3bd519c49ab489c58d93cb0b5b..00c1ac60309ac718e18964cc8ecaa4d66f4d4d84 100644
--- a/ash/display/display_controller.h
+++ b/ash/display/display_controller.h
@@ -147,11 +147,11 @@
   // Sets the work area's |insets| to the display assigned to |window|.
   bool UpdateWorkAreaOfDisplayNearestWindow(const aura::Window* window,
                                             const gfx::Insets& insets);
-  // gfx::DisplayObserver overrides:
+  // aura::DisplayObserver overrides:
+  virtual void OnDisplayBoundsChanged(
+      const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayAdded(const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayRemoved(const gfx::Display& display) OVERRIDE;
-  virtual void OnDisplayMetricsChanged(const gfx::Display& display,
-                                       uint32_t metrics) OVERRIDE;
 
   // aura::WindowTreeHostObserver overrides:
   virtual void OnHostResized(const aura::WindowTreeHost* host) OVERRIDE;