How to save runtime generated texture in Webplayer to hard drive?

So here is the deal: I am making smt like Paint app, and suddenly fall into problems with saving of drawing result in web-player.

i believe that it is possible to do with WWW class and some html / php (of course if server that hold web-player have some scripts to maintain it). but idea is to make something like standalone application. i mean you just put web-player into /www folder of your server, and everything works perfect without any additional options adjusting\scripts.

so, my first step was using example provided by EncodeToPNG docs.

if i run it as standalone app everything is perfect, but if it is web-player build - it throws error: 'WriteAllBytes' is not a member of 'System.IO.File'.

i found solution here and build web-player. but then when i am trying to save textures web-player gives error.

how to solve this problem without using server as a bump storage for textures? i believe it can be done by WWW class, but i don't know how, trying to solve it right now.

here is actual code of file save\creation

 // Encoding
 var bytes = tex.EncodeToPNG();
 var PathToTexture : String = FilePath +"/" + NameOfGameObject + ".png";
 // saving to hard drive
 var fs : FileStream = FileStream(PathToTexture, FileMode.CreateNew);
 var w : BinaryWriter = BinaryWriter(fs);
 w.Write(bytes);
 w.Close();
 fs.Close();

edit1: looks like official docs saying that saving to hard drive is disabled by security reasons. but how the hell others did it?? lol