Remember the configured device scale factor for external displays.

ash/display/display_info.cc

Index: ash/display/display_info.cc
diff --git a/ash/display/display_info.cc b/ash/display/display_info.cc
index bffaf3e3516f46353667354c16ef4fca4274b5f8..761f184743d5b2bc0e3a6016aaa22120edd1ce55 100644
--- a/ash/display/display_info.cc
+++ b/ash/display/display_info.cc
@@ -153,6 +153,14 @@ DisplayInfo DisplayInfo::CreateFromSpecWithID(const std::string& spec,
       std::string resolution = parts[i];
       int width, height;
       float refresh_rate = 0.0f;
+      float device_scale_factor = 1.0f;
+      size_t asterisk_pos = resolution.find("*");
+      if (asterisk_pos != std::string::npos) {
+        sscanf(resolution.substr(asterisk_pos + 1).c_str(),
+               "%f",
+               &device_scale_factor);
+        resolution = resolution.substr(0, asterisk_pos);
+      }
       if (sscanf(resolution.c_str(),
                  "%dx%d%%%f",
                  &width,
@@ -165,8 +173,9 @@ DisplayInfo DisplayInfo::CreateFromSpecWithID(const std::string& spec,
           highest_refresh_rate = refresh_rate;
           native_mode = i;
         }
-        display_modes.push_back(
-            DisplayMode(gfx::Size(width, height), refresh_rate, false, false));
+        DisplayMode mode(gfx::Size(width, height), refresh_rate, false, false);
+        mode.device_scale_factor = device_scale_factor;
+        display_modes.push_back(mode);
       }
     }
     display_modes[native_mode].native = true;