Refactor screen/monitor so that gfx::Screen returns monitor object.

ui/gfx/screen_impl.h

+// 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_GFX_SCREEN_IMPL_H_
+#define UI_GFX_SCREEN_IMPL_H_
+#pragma once
+
+#include "ui/gfx/native_widget_types.h"
+#include "ui/gfx/monitor.h"
+#include "ui/gfx/point.h"
+
+namespace gfx {
+
+// A class that provides |gfx::Screen|'s implementation on aura.
+class UI_EXPORT ScreenImpl {
+ public:
+  virtual ~ScreenImpl() {}
+
+  virtual gfx::Point GetCursorScreenPoint() = 0;
+  virtual gfx::NativeWindow GetWindowAtCursorScreenPoint() = 0;
+
+  virtual int GetNumMonitors() = 0;
+  virtual gfx::Monitor GetMonitorNearestWindow(
+      gfx::NativeView window) const = 0;
+  virtual gfx::Monitor GetMonitorNearestPoint(
+      const gfx::Point& point) const = 0;
+  virtual gfx::Monitor GetPrimaryMonitor() const = 0;
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_SCREEN_IMPL_H_