Make ash::DisplayMode more like ui::DisplayMode

ash/display/window_tree_host_manager.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 "ash/display/window_tree_host_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 #include <memory>
@@ skipping 118 matching lines @@
     scale *= kCursorMultiplierForExternalDisplays;
 
   ui::CursorController::GetInstance()->SetCursorConfigForWindow(
       host->GetAcceleratedWidget(), info.GetActiveRotation(), scale);
 #endif
 #endif
   std::unique_ptr<RootWindowTransformer> transformer(
       CreateRootWindowTransformerForDisplay(host->window(), display));
   ash_host->SetRootWindowTransformer(std::move(transformer));
 
-  DisplayMode mode =
+  scoped_refptr<DisplayMode> mode =
       GetDisplayManager()->GetActiveModeForDisplayId(display.id());
-  if (mode.refresh_rate > 0.0f) {
+  if (mode && mode->refresh_rate() > 0.0f) {
     host->compositor()->SetAuthoritativeVSyncInterval(
         base::TimeDelta::FromMicroseconds(base::Time::kMicrosecondsPerSecond /
-                                          mode.refresh_rate));
+                                          mode->refresh_rate()));
   }
 
   // Just movnig the display requires the full redraw.
   // chrome-os-partner:33558.
   host->compositor()->ScheduleFullRedraw();
 }
 
 void ClearDisplayPropertiesOnHost(AshWindowTreeHost* ash_host) {
 #if defined(OS_CHROMEOS) && defined(USE_OZONE)
   aura::WindowTreeHost* host = ash_host->AsWindowTreeHost();
@@ skipping 690 matching lines @@
   SetDisplayPropertiesOnHost(ash_host, display);
 
 #if defined(OS_CHROMEOS)
   if (switches::ConstrainPointerToRoot())
     ash_host->ConfineCursorToRootWindow();
 #endif
   return ash_host;
 }
 
 }  // namespace ash