Get the default device scale factor from monitor

ui/aura/monitor_change_observer_x11.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_change_observer_x11.h"
 
 #include <algorithm>
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 46 matching lines @@
 bool MonitorChangeObserverX11::Dispatch(const base::NativeEvent& event) {
   if (event->type - xrandr_event_base_ == RRScreenChangeNotify) {
     NotifyMonitorChange();
   }
   return true;
 }
 
 void MonitorChangeObserverX11::NotifyMonitorChange() {
   if (!MonitorManager::use_fullscreen_host_window())
     return;  // Use the default monitor that monitor manager determined.
+  float default_device_scale_factor =
+      Env::GetInstance()->monitor_manager()->default_device_scale_factor();
 
   XRRScreenResources* screen_resources =
       XRRGetScreenResources(xdisplay_, x_root_window_);
   std::map<XID, XRRCrtcInfo*> crtc_info_map;
 
   for (int c = 0; c < screen_resources->ncrtc; c++) {
     XID crtc_id = screen_resources->crtcs[c];
     XRRCrtcInfo *crtc_info =
         XRRGetCrtcInfo(xdisplay_, screen_resources, crtc_id);
     crtc_info_map[crtc_id] = crtc_info;
@@ skipping 17 matching lines @@
     }
     XRRModeInfo* mode = FindMode(screen_resources, crtc_info->mode);
     CHECK(mode);
     // Mirrored monitors have the same y coordinates.
     if (y_coords.find(crtc_info->y) != y_coords.end())
       continue;
     // TODO(oshima): Create unique ID for the monitor.
     monitors.push_back(gfx::Monitor(
         0,
         gfx::Rect(crtc_info->x, crtc_info->y, mode->width, mode->height)));
+    monitors.back().set_device_scale_factor(default_device_scale_factor);
     y_coords.insert(crtc_info->y);
     XRRFreeOutputInfo(output_info);
   }
 
   // Free all allocated resources.
   for (std::map<XID, XRRCrtcInfo*>::const_iterator iter = crtc_info_map.begin();
        iter != crtc_info_map.end(); ++iter) {
     XRRFreeCrtcInfo(iter->second);
   }
   XRRFreeScreenResources(screen_resources);
 
   // PowerManager lays out the outputs vertically. Sort them by Y
   // coordinates.
   std::sort(monitors.begin(), monitors.end(), CompareMonitorY);
   // TODO(oshima): Assisgn index as ID for now. Use unique ID.
   int id = 0;
   for (std::vector<gfx::Monitor>::iterator iter = monitors.begin();
        iter != monitors.end(); ++iter, ++id)
     (*iter).set_id(id);
 
   Env::GetInstance()->monitor_manager()
       ->OnNativeMonitorsChanged(monitors);
 }
 
 }  // namespace internal
 }  // namespace aura