Flip the flag to enable smooth screen rotation by default.

ash/rotator/test/screen_rotation_animator_test_api.cc

Index: ash/rotator/test/screen_rotation_animator_test_api.cc
diff --git a/ash/rotator/test/screen_rotation_animator_test_api.cc b/ash/rotator/test/screen_rotation_animator_test_api.cc
index 0d3d679a61f9aee00942e564b80691bd20921205..eef973cc1657a981f60041928e5ef1dbe8aee7fe 100644
--- a/ash/rotator/test/screen_rotation_animator_test_api.cc
+++ b/ash/rotator/test/screen_rotation_animator_test_api.cc
@@ -21,6 +21,10 @@ void ScreenRotationAnimatorTestApi::DisableAnimationTimers() {
   animator_->set_disable_animation_timers_for_test(true);
 }
 
+void ScreenRotationAnimatorTestApi::SetEnableAnimation(bool enable) {
+  animator_->set_enable_animation_for_test(enable);
+}
+
 std::vector<ui::LayerAnimator*>
 ScreenRotationAnimatorTestApi::GetLayerAnimators() {
   std::vector<ui::LayerAnimator*> animators;