Remember the configured device scale factor for external displays.

chrome/browser/chromeos/display/display_preferences.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 "chrome/browser/chromeos/display/display_preferences.h"
 
 #include "ash/display/display_layout_store.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/display_pref_util.h"
 #include "ash/shell.h"
@@ skipping 148 matching lines @@
     }
     int ui_scale_value = 0;
     if (dict_value->GetInteger("ui-scale", &ui_scale_value))
       ui_scale = static_cast<float>(ui_scale_value) / 1000.0f;
 
     int width = 0, height = 0;
     dict_value->GetInteger("width", &width);
     dict_value->GetInteger("height", &height);
     gfx::Size resolution_in_pixels(width, height);
 
+    float device_scale_factor = 1.0;
+    int dsf_value = 0;
+    if (dict_value->GetInteger("device-scale-factor", &dsf_value))
+      device_scale_factor = static_cast<float>(dsf_value) / 1000.0f;
+
     gfx::Insets insets;
     if (ValueToInsets(*dict_value, &insets))
       insets_to_set = &insets;
 
     ui::ColorCalibrationProfile color_profile = ui::COLOR_PROFILE_STANDARD;
     std::string color_profile_name;
     if (dict_value->GetString("color_profile_name", &color_profile_name))
       color_profile = StringToColorProfile(color_profile_name);
     GetDisplayManager()->RegisterDisplayProperty(id,
                                                  rotation,
                                                  ui_scale,
                                                  insets_to_set,
                                                  resolution_in_pixels,
+                                                 device_scale_factor,
                                                  color_profile);
   }
 }
 
 void StoreDisplayLayoutPref(const ash::DisplayIdPair& pair,
                             const ash::DisplayLayout& display_layout) {
   std::string name =
       base::Int64ToString(pair.first) + "," + base::Int64ToString(pair.second);
 
   PrefService* local_state = g_browser_process->local_state();
@@ skipping 39 matching lines @@
     property_value->SetInteger("rotation", static_cast<int>(info.rotation()));
     property_value->SetInteger(
         "ui-scale",
         static_cast<int>(info.configured_ui_scale() * 1000));
     ash::DisplayMode mode;
     if (!display.IsInternal() &&
         display_manager->GetSelectedModeForDisplayId(id, &mode) &&
         !mode.native) {
       property_value->SetInteger("width", mode.size.width());
       property_value->SetInteger("height", mode.size.height());
+      property_value->SetInteger(
+          "device-scale-factor",
+          static_cast<int>(mode.device_scale_factor * 1000));
     }
     if (!info.overscan_insets_in_dip().empty())
       InsetsToValue(info.overscan_insets_in_dip(), property_value.get());
     if (info.color_profile() != ui::COLOR_PROFILE_STANDARD) {
       property_value->SetString(
           "color_profile_name", ColorProfileToString(info.color_profile()));
     }
     pref_data->Set(base::Int64ToString(id), property_value.release());
   }
 }
@@ skipping 86 matching lines @@
                                    const ash::DisplayLayout& layout) {
   StoreDisplayLayoutPref(std::make_pair(id1, id2), layout);
 }
 
 // Stores the given |power_state|.
 void StoreDisplayPowerStateForTest(DisplayPowerState power_state) {
   StoreDisplayPowerState(power_state);
 }
 
 }  // namespace chromeos