Animation created via script does not play

I have created an empty GameObject and assigned it a script:

 [MenuItem("Custom workflow/Initialize")]
 static void Initialize()
 {
     // Place a text mesh on the scene
     var obj = new GameObject("Sample");
     obj.transform.position = new Vector3(0, 0, 0);
     var text = obj.AddComponent<TextMesh>();
     text.text = "Hello world";

     AnimationClip clip1 = CreateAnimationClip();
     AnimatorController sm = CreateSimpleAnimatorController(clip1);

     var animator = obj.AddComponent<Animator>();
     animator.runtimeAnimatorController = sm;
     animator.applyRootMotion = true;
 }

In the same file, I have created method CreateAnimationClip:

 private static AnimationClip CreateAnimationClip()
 {
     var translateX = AnimationCurve.Linear(0.0f, 0.0f, 2.0f, 25.0f);
     var animationClip = new AnimationClip();
     animationClip.SetCurve("", typeof(Transform), "position.x", translateX);

     AssetDatabase.CreateAsset(animationClip, "Assets/procanim.anim");

     return animationClip;
 }

And I have also defined CreateSimpleAnimatorController:

 private static AnimatorController CreateSimpleAnimatorController(
   Motion motion1 = null, Motion motion2 = null)
 {
     // Creates the controller
     var controller = AnimatorController.CreateAnimatorControllerAtPath(
       "Assets/SimpleStateMachineTransitions.controller");

     // Add parameters
     controller.AddParameter("GoToB", AnimatorControllerParameterType.Bool);
     controller.AddParameter("GoToA", AnimatorControllerParameterType.Bool);

     // Add StateMachines
     var rootStateMachine = controller.layers[0].stateMachine;

     // Add States
     var stateA1 = rootStateMachine.AddState("stateA1");
     stateA1.motion = motion1;
     var stateB1 = rootStateMachine.AddState("stateB1");
     stateB1.motion = motion2;

     // Add Transitions
     var transitionAB = stateA1.AddTransition(stateB1);
     transitionAB.AddCondition(AnimatorConditionMode.If, 0, "GoToB");
     transitionAB.duration = 0;

     var transitionBA = stateB1.AddTransition(stateA1);
     transitionBA.AddCondition(AnimatorConditionMode.If, 0, "GoToA");
     transitionBA.duration = 0;

     return controller;
 }

The problem

As I invoke the menu item, I get all assets in place. When I hit play, nothing happens. I can see state stateA1 is on, but the animation does not run. If I click on the text object in the scene, this is what I see in the animation window:

I think the problem might be here:

 animationClip.SetCurve("", typeof(Transform), "position.x", translateX);

Because when I remove it manually and add it manually using the interface and hit play again, it works.