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

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 036c00f0a40b8b687726127af33cdb56d18ff539..f5fbaa4ae95dea0495553ec4dfddac326b8b3ae8 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -76,7 +76,7 @@
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/env.h"
 #include "ui/aura/layout_manager.h"
-#include "ui/aura/monitor.h"
+#include "ui/aura/monitor_aura.h"
 #include "ui/aura/monitor_manager.h"
 #include "ui/aura/monitor_manager.h"
 #include "ui/aura/root_window.h"
@@ -84,6 +84,7 @@
 #include "ui/aura/window.h"
 #include "ui/gfx/compositor/layer.h"
 #include "ui/gfx/compositor/layer_animator.h"
+#include "ui/gfx/screen.h"
 #include "ui/gfx/size.h"
 #include "ui/ui_controls/ui_controls.h"
 #include "ui/views/widget/native_widget_aura.h"
@@ -842,7 +843,7 @@ void Shell::RotateFocus(Direction direction) {
 
 void Shell::SetMonitorWorkAreaInsets(Window* contains,
                                      const gfx::Insets& insets) {
-  aura::Monitor* monitor = aura::Env::GetInstance()->monitor_manager()->
+  aura::MonitorAura* monitor = aura::Env::GetInstance()->monitor_manager()->
       GetMonitorNearestWindow(contains);
   if (monitor->work_area_insets() == insets)
     return;