Fixed the ScreenOrientationController so that it doesn't crash by animating

ash/rotator/screen_rotation_animator.cc

Index: ash/rotator/screen_rotation_animator.cc
diff --git a/ash/rotator/screen_rotation_animator.cc b/ash/rotator/screen_rotation_animator.cc
index ed37b7f1da31bb7d519193ea8c29d999fb91e8a8..3d32e87642ee12412c893fc628b911c42f735f7b 100644
--- a/ash/rotator/screen_rotation_animator.cc
+++ b/ash/rotator/screen_rotation_animator.cc
@@ -267,6 +267,13 @@ ScreenRotationAnimator::ScreenRotationAnimator(int64 display_id)
 ScreenRotationAnimator::~ScreenRotationAnimator() {
 }
 
+bool ScreenRotationAnimator::CanAnimate() const {
+  return Shell::GetInstance()
+      ->display_manager()
+      ->GetDisplayForId(display_id_)
+      .is_valid();
+}
+
 void ScreenRotationAnimator::Rotate(gfx::Display::Rotation new_rotation) {
   const gfx::Display::Rotation current_rotation =
       GetCurrentRotation(display_id_);