TestWindow by M.S.

using UnityEngine;
using System.Collections;
using UnityEditor;

public class TestWindow : EditorWindow {

	public GameObject target;
	public AnimationClip idleAnim;
	public AnimationClip walkAnim;
	public AnimationClip runAnim;

	// Use this for initialization
	void Start () {

	}

	[MenuItem ("Window/Animation Helper")]
	static void OpenWindow () {
		// Get existing open window or if none, make a new one:
		EditorWindow.GetWindow(typeof(TestWindow));

	}

	void OnGUI()
	{
		target = EditorGUILayout.ObjectField("Target Object", target, typeof(GameObject), true) as GameObject;
		idleAnim = EditorGUILayout.ObjectField("Idle", idleAnim, typeof(AnimationClip), true) as AnimationClip;
		walkAnim = EditorGUILayout.ObjectField("Walk", walkAnim, typeof(AnimationClip), true) as AnimationClip;
		runAnim = EditorGUILayout.ObjectField("Run", runAnim, typeof(AnimationClip), true) as AnimationClip;

		if (GUILayout.Button("Create"))
		{
			UnityEditor.Animations.AnimatorController controller = UnityEditor.Animations.AnimatorController.CreateAnimatorControllerAtPath("Assets/" + target.name + ".controller");

			// Adds 2 parameters
			controller.AddParameter("Speed", UnityEngine.AnimatorControllerParameterType.Float);

			//Add states
			UnityEditor.Animations.AnimatorState idleState = controller.layers[0].stateMachine.AddState("Idle");
			idleState.motion = idleAnim;

			// Blend Tree creation
			UnityEditor.Animations.BlendTree blendTree;
			UnityEditor.Animations.AnimatorState moveState = controller.CreateBlendTreeInController("Move", out blendTree);

			// BlendTree setup
			blendTree.blendType = UnityEditor.Animations.BlendTreeType.Simple1D;
			blendTree.blendParameter = "Speed";
			blendTree.AddChild(walkAnim);
			blendTree.AddChild(runAnim);

			UnityEditor.Animations.AnimatorStateTransition leaveIdle = idleState.AddTransition(moveState);
			UnityEditor.Animations.AnimatorStateTransition leaveMove = moveState.AddTransition(idleState);

			leaveIdle.AddCondition(UnityEditor.Animations.AnimatorConditionMode.Less, 0.01f, "Speed");
			leaveMove.AddCondition(UnityEditor.Animations.AnimatorConditionMode.Greater, 0.01f, "Speed");

			target.GetComponent<Animator>().runtimeAnimatorController = controller;
			}

	}

	// Update is called once per frame
	void Update () {

	}
}