Flip the flag to enable smooth screen rotation by default.

ash/test/display_configuration_controller_test_api.cc

Index: ash/test/display_configuration_controller_test_api.cc
diff --git a/ash/test/display_configuration_controller_test_api.cc b/ash/test/display_configuration_controller_test_api.cc
index 0c95897992c130119965272d4022b19cddc2d515..3e485c5f9878292c3068135306ee73102eaf166a 100644
--- a/ash/test/display_configuration_controller_test_api.cc
+++ b/ash/test/display_configuration_controller_test_api.cc
@@ -5,6 +5,7 @@
 #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 {
@@ -28,5 +29,13 @@ DisplayConfigurationControllerTestApi::GetScreenRotationAnimatorForDisplay(
   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