Use a universally supported library for file picking

Assets/Plugins/SimpleFileBrowser/Android/FBCallbackHelper.cs

@@ -0,0 +1,52 @@
+#if UNITY_EDITOR || UNITY_ANDROID
+using System;
+using UnityEngine;
+
+namespace SimpleFileBrowser
+{
+	public class FBCallbackHelper : MonoBehaviour
+	{
+		private bool autoDestroyWithCallback;
+		private Action mainThreadAction = null;
+
+		public static FBCallbackHelper Create( bool autoDestroyWithCallback )
+		{
+			FBCallbackHelper result = new GameObject( "FBCallbackHelper" ).AddComponent<FBCallbackHelper>();
+			result.autoDestroyWithCallback = autoDestroyWithCallback;
+			DontDestroyOnLoad( result.gameObject );
+			return result;
+		}
+
+		public void CallOnMainThread( Action function )
+		{
+			lock( this )
+			{
+				mainThreadAction += function;
+			}
+		}
+
+		private void Update()
+		{
+			if( mainThreadAction != null )
+			{
+				try
+				{
+					Action temp;
+					lock( this )
+					{
+						temp = mainThreadAction;
+						mainThreadAction = null;
+					}
+
+					temp();
+				}
+				finally
+				{
+					if( autoDestroyWithCallback )
+						Destroy( gameObject );
+				}
+			}
+		}
+	}
+}
+#endif