Remember the configured device scale factor for external displays.

ash/display/display_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/display_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 #include <string>
@@ skipping 512 matching lines @@
 #endif
   return resolution_changed;
 }
 
 void DisplayManager::RegisterDisplayProperty(
     int64 display_id,
     gfx::Display::Rotation rotation,
     float ui_scale,
     const gfx::Insets* overscan_insets,
     const gfx::Size& resolution_in_pixels,
+    float device_scale_factor,
     ui::ColorCalibrationProfile color_profile) {
   if (display_info_.find(display_id) == display_info_.end())
     display_info_[display_id] = DisplayInfo(display_id, std::string(), false);
 
   display_info_[display_id].set_rotation(rotation);
   display_info_[display_id].SetColorProfile(color_profile);
   // Just in case the preference file was corrupted.
   // TODO(mukai): register |display_modes_| here as well, so the lookup for the
   // default mode in GetActiveModeForDisplayId() gets much simpler.
   if (0.5f <= ui_scale && ui_scale <= 2.0f)
     display_info_[display_id].set_configured_ui_scale(ui_scale);
   if (overscan_insets)
     display_info_[display_id].SetOverscanInsets(*overscan_insets);
   if (!resolution_in_pixels.IsEmpty()) {
+    DCHECK(!IsInternalDisplayId(display_id));
     // Default refresh rate, until OnNativeDisplaysChanged() updates us with the
     // actual display info, is 60 Hz.
-    display_modes_[display_id] =
-        DisplayMode(resolution_in_pixels, 60.0f, false, false);
+    DisplayMode mode(resolution_in_pixels, 60.0f, false, false);
+    mode.device_scale_factor = device_scale_factor;
+    display_modes_[display_id] = mode;
   }
 }
 
 DisplayMode DisplayManager::GetActiveModeForDisplayId(int64 display_id) const {
   DisplayMode selected_mode;
   if (GetSelectedModeForDisplayId(display_id, &selected_mode))
     return selected_mode;
 
   // If 'selected' mode is empty, it should return the default mode. This means
   // the native mode for the external display. Unfortunately this is not true
@@ skipping 667 matching lines @@
       new_secondary_origin.Offset(-secondary_bounds.width(), offset);
       break;
   }
   gfx::Insets insets = secondary_display->GetWorkAreaInsets();
   secondary_display->set_bounds(
       gfx::Rect(new_secondary_origin, secondary_bounds.size()));
   secondary_display->UpdateWorkAreaFromInsets(insets);
 }
 
 }  // namespace ash