Get the default device scale factor from monitor

ui/aura/monitor_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 "ui/aura/monitor_manager.h"
 
 #include <stdio.h>
 
 #include "base/logging.h"
 #include "ui/aura/env.h"
@@ skipping 14 matching lines @@
 
 // static
 bool MonitorManager::use_fullscreen_host_window_ = false;
 
 // static
 gfx::Monitor MonitorManager::CreateMonitorFromSpec(const std::string& spec) {
   static int synthesized_monitor_id = 1000;
   gfx::Rect bounds(kDefaultHostWindowX, kDefaultHostWindowY,
                    kDefaultHostWindowWidth, kDefaultHostWindowHeight);
   int x = 0, y = 0, width, height;
-  float scale = 1.0f;
+  float scale = gfx::Monitor::GetDefaultDeviceScaleFactor();
   if (sscanf(spec.c_str(), "%dx%d*%f", &width, &height, &scale) >= 2) {
     bounds.set_size(gfx::Size(width, height));
   } else if (sscanf(spec.c_str(), "%d+%d-%dx%d*%f", &x, &y, &width, &height,
                     &scale) >= 4 ) {
     bounds = gfx::Rect(x, y, width, height);
   } else if (use_fullscreen_host_window_) {
     bounds = gfx::Rect(aura::RootWindowHost::GetNativeScreenSize());
   }
   gfx::Monitor monitor(synthesized_monitor_id++);
   monitor.SetScaleAndBounds(scale, bounds);
@@ skipping 34 matching lines @@
   FOR_EACH_OBSERVER(MonitorObserver, observers_,
                     OnMonitorAdded(monitor));
 }
 
 void MonitorManager::NotifyMonitorRemoved(const gfx::Monitor& monitor) {
   FOR_EACH_OBSERVER(MonitorObserver, observers_,
                     OnMonitorRemoved(monitor));
 }
 
 }  // namespace aura