Flip the flag to enable smooth screen rotation by default.

ash/display/display_configuration_controller.cc

Index: ash/display/display_configuration_controller.cc
diff --git a/ash/display/display_configuration_controller.cc b/ash/display/display_configuration_controller.cc
index 29cd68edca1826eb438ec3e3dc3e97f7291f5258..54c43a7f398206e2fe421fe604d60e7603004978 100644
--- a/ash/display/display_configuration_controller.cc
+++ b/ash/display/display_configuration_controller.cc
@@ -31,6 +31,14 @@ const int64_t kSetPrimaryDisplayThrottleTimeoutMs = 500;
 
 namespace ash {
 
+namespace {
+
+bool CanAnimate(ScreenRotationAnimator* animator) {
+  return animator && animator->CanAnimate();
+}
+
+}  // namespace
+
 class DisplayConfigurationController::DisplayChangeLimiter {
  public:
   DisplayChangeLimiter() : throttle_timeout_(base::Time::Now()) {}
@@ -104,12 +112,13 @@ void DisplayConfigurationController::SetDisplayRotation(
       rotation)
     return;
 
+  ScreenRotationAnimator* screen_rotation_animator = nullptr;
   if (display_manager_->IsDisplayIdValid(display_id)) {
-    ScreenRotationAnimator* screen_rotation_animator =
-        GetScreenRotationAnimatorForDisplay(display_id);
+    screen_rotation_animator = GetScreenRotationAnimatorForDisplay(display_id);
+  }
+  if (CanAnimate(screen_rotation_animator)) {
     screen_rotation_animator->Rotate(rotation, source);
   } else {
-    DCHECK(!rotation_animator_map_.count(display_id));
     display_manager_->SetDisplayRotation(display_id, rotation, source);
   }
 }