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

ui/aura/monitor_aura.cc

+// 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.
+
+#include "ui/aura/monitor_aura.h"
+
+namespace aura {
+
+MonitorAura::MonitorAura() : device_scale_factor_(1.0f) {
+}
+
+MonitorAura::~MonitorAura() {
+}
+
+gfx::Rect MonitorAura::GetBounds() const {
+  // TODO(oshima): For m19, the origin of work area/monitor bounds for
+  // views/aura is always (0,0) because it's simple and enough. Fix this when
+  // real multi monitor support is implemented.
+  return gfx::Rect(bounds_.size());
+}
+
+gfx::Rect MonitorAura::GetWorkArea() const {
+  // TODO(oshima): For m19, work area/monitor bounds has (0,0) origin
+  // because it's simpler and enough. Fix this when real multi monitor
+  // support is implemented.
+  gfx::Rect bounds(bounds_.size());
+  bounds.Inset(work_area_insets_);
+  return bounds;
+}
+
+float MonitorAura::GetDeviceScaleFactor() const {
+  return device_scale_factor_;
+}
+
+}  // namespace aura