Flip the flag to enable smooth screen rotation by default.

ash/test/display_configuration_controller_test_api.cc

 // Copyright 2017 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/test/display_configuration_controller_test_api.h"
 
 #include "ash/display/display_configuration_controller.h"
+#include "ash/rotator/test/screen_rotation_animator_test_api.h"
 
 namespace ash {
 namespace test {
 
 DisplayConfigurationControllerTestApi::DisplayConfigurationControllerTestApi(
     DisplayConfigurationController* controller)
     : controller_(controller) {}
 
 void DisplayConfigurationControllerTestApi::DisableDisplayAnimator() {
   controller_->ResetAnimatorForTest();
 }
 
 int DisplayConfigurationControllerTestApi::
     DisplayScreenRotationAnimatorMapSize() {
   return controller_->rotation_animator_map_.size();
 }
 
 ScreenRotationAnimator*
 DisplayConfigurationControllerTestApi::GetScreenRotationAnimatorForDisplay(
     int64_t display_id) {
   return controller_->GetScreenRotationAnimatorForDisplay(display_id);
 }
 
+void DisplayConfigurationControllerTestApi::SetEnableScreenRotationAnimator(
+    int64_t display_id,
+    bool enable) {
+  ScreenRotationAnimatorTestApi test_api(
+      controller_->GetScreenRotationAnimatorForDisplay(display_id));
+  test_api.SetEnableAnimation(enable);
+}
+
 }  // namespace test
 }  // namespace ash