Fix errors in display resolution change notifications

ui/display/manager/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 "ui/display/manager/display_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <map>
@@ skipping 359 matching lines @@
         return false;
       }
 
       if (change_ui_scale) {
         if (info.configured_ui_scale() == display_mode->ui_scale())
           return true;
         info.set_configured_ui_scale(display_mode->ui_scale());
         display_property_changed = true;
       } else {
         display_modes_[display_id] = *iter;
-        if (info.bounds_in_native().size() != display_mode->size())
+        if (info.bounds_in_native().size() != display_mode->size()) {
+          // If resolution changes, then we can break right here. No need to
+          // continue to fill |display_info_list|, since we won't be
+          // synchronously updating the displays here.
           resolution_changed = true;
+          break;
+        }
         if (info.device_scale_factor() != display_mode->device_scale_factor()) {
           info.set_device_scale_factor(display_mode->device_scale_factor());
           display_property_changed = true;
         }
       }
     }
-    display_info_list.push_back(info);
+    display_info_list.emplace_back(info);
   }
-  if (display_property_changed) {
+
+  if (display_property_changed && !resolution_changed) {
+    // We shouldn't synchronously update the displays here if the resolution
+    // changed. This should happen asynchronously when configuration is
+    // triggered.
     AddMirrorDisplayInfoIfAny(&display_info_list);
     UpdateDisplaysWith(display_info_list);
   }
-  if (resolution_changed && IsInUnifiedMode()) {
+
+  if (resolution_changed && IsInUnifiedMode())
     ReconfigureDisplays();
 #if defined(OS_CHROMEOS)
-  } else if (resolution_changed && configure_displays_) {
+  else if (resolution_changed && configure_displays_)
     delegate_->display_configurator()->OnConfigurationChanged();
-#endif
-  }
+#endif  // defined(OS_CHROMEOS)
+
   return resolution_changed || display_property_changed;
 }
 
 void DisplayManager::RegisterDisplayProperty(
     int64_t display_id,
     Display::Rotation rotation,
     float ui_scale,
     const gfx::Insets* overscan_insets,
     const gfx::Size& resolution_in_pixels,
     float device_scale_factor,
@@ skipping 1069 matching lines @@
 }
 
 const Display& DisplayManager::GetSecondaryDisplay() const {
   CHECK_LE(2U, GetNumDisplays());
   return GetDisplayAt(0).id() == Screen::GetScreen()->GetPrimaryDisplay().id()
              ? GetDisplayAt(1)
              : GetDisplayAt(0);
 }
 
 }  // namespace display