Work with Animation Clips embedded in an AnimatorController asset

EmbeddedAnimationClipUtility.cs

using System.Linq;
using UnityEditor;
using UnityEditor.Animations;
using UnityEngine;

namespace com.hololabs
{
    public static class EmbeddedAnimationClipUtility
    {
        [MenuItem("Assets/Add Embedded Animation Clip", false)]
        public static void AddEmbeddedClip()
        {
            var container = Selection.activeObject as AnimatorController;
            if (!container) return;
            TextInputDialog.Prompt("New clip",
                "Name for new embedded clip:",
                name =>
                {
                    AssetDatabase.AddObjectToAsset(new AnimationClip {name = name}, container);
                    AssetDatabase.SaveAssets();
                    AssetDatabase.Refresh();
                    Debug.Log("Done");
                });
        }

        [MenuItem("Assets/Add Embedded Animation Clip", true)]
        public static bool AddEmbeddedClip_Validate()
        {
            Object obj = Selection.activeObject;
            return (obj && obj is AnimatorController && AssetDatabase.Contains(obj));
        }

        [MenuItem("Assets/Remove Embedded Animation Clip", false)]
        public static void RemoveEmbeddedClip()
        {
            foreach (Object clip in Selection.objects)
            {
                Object.DestroyImmediate(clip, true);
            }
            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
            Debug.Log("Done");
        }

        [MenuItem("Assets/Remove Embedded Animation Clip", true)]
        public static bool RemoveEmbeddedClip_Validate()
        {
            return Selection.objects.All(obj => obj && obj is AnimationClip && AssetDatabase.Contains(obj) && AssetDatabase.IsSubAsset(obj));
        }
    }
}

TextInputDialog.cs

using System;
using UnityEditor;
using UnityEngine;

namespace com.hololabs
{
    public class TextInputDialog : EditorWindow
    {
        const string INPUT_NAME = "TextInputDialog_TextField";
        public string promptText = "Enter your input:";
        public Action<string> callback;

        void OnGUI()
        {
            EditorGUILayout.BeginVertical(GUIStyle.none, GUILayout.ExpandHeight(true), GUILayout.ExpandWidth(true));
            EditorGUILayout.LabelField(promptText);
            GUI.SetNextControlName(INPUT_NAME);
            string inputText = EditorGUILayout.DelayedTextField("");
            EditorGUILayout.EndVertical();

            if (string.IsNullOrEmpty(inputText))
            {
                EditorGUI.FocusTextInControl(INPUT_NAME);
            }
            else
            {
                callback(inputText);
                Close();
            }
        }

        void OnLostFocus()
        {
            Close();
        }

        public static void Prompt(string title, string promptText, Action<string> callback)
        {
            var window = CreateInstance<TextInputDialog>();
            window.minSize = new Vector2(300, 50);
            window.maxSize = window.minSize;
            window.titleContent = new GUIContent(title);
            window.callback = callback;
            window.promptText = promptText;
            window.ShowUtility();
        }
    }
}