Fix errors in display resolution change notifications

chrome/browser/ui/webui/options/chromeos/display_options_handler.cc

Index: chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
diff --git a/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc b/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
index 297d54326916649163d325b92753837f5ffa1899..4b9a7a3b17d5721bf6e17ad9ab25320859c37341 100644
--- a/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
+++ b/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
@@ -491,19 +491,28 @@ void DisplayOptionsHandler::HandleSetDisplayMode(const base::ListValue* args) {
   display::DisplayManager* display_manager = GetDisplayManager();
   scoped_refptr<display::ManagedDisplayMode> current_mode =
       display_manager->GetActiveModeForDisplayId(display_id);
+
+  if (mode->IsEquivalent(current_mode)) {
+    LOG(ERROR) << "New display mode matches current mode.";
+    return;
+  }
+
+  // We must prepare the notification before we set the mode, since setting
+  // the mode actually shows the notification, so it should be ready by then.
+  // crbug.com/701389.
+  if (display::Display::IsInternalDisplayId(display_id)) {
+    // For external displays, show a notification confirming the resolution
+    // change.
+    ash::Shell::GetInstance()
+        ->resolution_notification_controller()
+        ->PrepareNotification(display_id, current_mode, mode,
+                              base::Bind(&chromeos::StoreDisplayPrefs));
+  }
+
   if (!display_manager->SetDisplayMode(display_id, mode)) {
     LOG(ERROR) << "Unable to set display mode for: " << display_id
                << " Mode: " << *mode_data;
-    return;
   }
-  if (display::Display::IsInternalDisplayId(display_id))
-    return;
-  // For external displays, show a notification confirming the resolution
-  // change.
-  ash::Shell::GetInstance()
-      ->resolution_notification_controller()
-      ->PrepareNotification(display_id, current_mode, mode,
-                            base::Bind(&chromeos::StoreDisplayPrefs));
 }
 
 void DisplayOptionsHandler::HandleSetRotation(const base::ListValue* args) {