title: PNG file displayed as red question mark after download with HttpWebRequest
body: <p>I face the following issue: I downloading a png file from google drive, all bytes are successfully received (as it seems), but when I try to construct a <code>Texture2D</code> and set it as <code>Sprite</code> in an <code>Image</code>, only red a question mark appears.</p>
  
  <p>Am I missing something?</p>
  
  <p>Code below:</p>
  
  <pre><code>HttpWebRequest request = (HttpWebRequest) WebRequest.Create("https://content.googleapis.com/drive/v3/files/" + fileId + "?alt=media");
  request.Method = "GET";
  request.ContentType = "image/png";
  request.Headers.Add("Authorization", "Bearer " + AUTH_TOKEN);
  
  WebResponse response = request.GetResponse();
  byte[] bytes = new byte[response.ContentLength];
  response.GetResponseStream().Read(bytes, 0, (int) response.ContentLength);
  response.Close();
  
  Texture2D texture2d = new Texture2D(8, 8);
  Sprite sprite = null;
  if (texture2d.LoadImage(bytes)) {
      sprite = Sprite.Create(texture2d, new Rect(0, 0, texture2d.width, texture2d.height), Vector2.zero);
  }
  if (sprite != null) {
      imageToUpdate.sprite = sprite;
  }
  </code></pre>