Preserve the native mode when parsing external display modes

ash/display/display_change_observer_chromeos.cc

 // Copyright 2013 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_change_observer_chromeos.h"
 
 #include <algorithm>
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 118 matching lines @@
       display_mode_it->second = display_mode;
   }
 
   std::vector<DisplayMode> display_mode_list;
   for (DisplayModeMap::const_iterator iter = display_mode_map.begin();
        iter != display_mode_map.end();
        ++iter) {
     display_mode_list.push_back(iter->second);
   }
 
+  if (output.display->native_mode()) {
+    const std::pair<int, int> size(native_mode.size.width(),
+                                   native_mode.size.height());
+    DisplayModeMap::iterator it = display_mode_map.find(size);
+    DCHECK(it != display_mode_map.end())
+        << "Native mode must be part of the mode list.";
+
+    // If the native mode was replaced re-add it.
+    if (!it->second.native)
+      display_mode_list.push_back(native_mode);
+  }
+
   if (native_mode.size.width() >= kMinimumWidthFor4K) {
     for (size_t i = 0; i < arraysize(kAdditionalDeviceScaleFactorsFor4k);
          ++i) {
       DisplayMode mode = native_mode;
       mode.device_scale_factor = kAdditionalDeviceScaleFactorsFor4k[i];
       mode.native = false;
       display_mode_list.push_back(mode);
     }
   }
 
@@ skipping 125 matching lines @@
   }
   return 1.0f;
 }
 
 void DisplayChangeObserver::OnInputDeviceConfigurationChanged() {
   OnDisplayModeChanged(
       Shell::GetInstance()->display_configurator()->cached_displays());
 }
 
 }  // namespace ash