Move Screen, its impls, DisplayObserver and DisplayChangeNotifier to ui/display

ui/display/display_observer.h

-// Copyright 2016 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_DISPLAY_DISPLAY_OBSERVER_H_
 #define UI_DISPLAY_DISPLAY_OBSERVER_H_
 
-#include "ui/gfx/display_observer.h"
+#include <stdint.h>
+
+#include "ui/display/display_export.h"
+
+namespace gfx {
+class Display;
+}
 
 namespace display {
 using Display = gfx::Display;
 
-// TODO(oshima): move the gfx::DisplayObserver to display::DisplayObserver.
-using DisplayObserver = gfx::DisplayObserver;
+// Observers for display configuration changes.
+// TODO(oshima): consolidate |WorkAreaWatcherObserver| and
+// |DisplaySettingsProvier|. crbug.com/122863.
+class DISPLAY_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,
+    DISPLAY_METRIC_PRIMARY = 1 << 4,
+  };
 
-}  // display
+  // 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();
+};
+
+}  // namespace display
 
 #endif  // UI_DISPLAY_DISPLAY_OBSERVER_H_