function jstLoadTemplate_(doc, html, targetId) {
  var existing_target = domGetElementById(doc, targetId);
  var target;
  if (!existing_target) {
    target = domCreateElement(doc, STRING_div);
    target.id = targetId;
    displayNone(target);
    positionAbsolute(target);
    domAppendChild(doc.body, target);
  } else {
    target = existing_target;
  }
  var div = domCreateElement(doc, STRING_div);
  target.appendChild(div);
  div.innerHTML = html;
}
Loads the given HTML text into the given document, so that
jstGetTemplate can find it.

We append it to the element identified by targetId, which is hidden.
If it doesn't exist, it is created.

@param {Document} doc The document to create the template in.

@param {string} html HTML text to be inserted into the document.

@param {string} targetId The id of a DOM object under which to attach the
  HTML once it's inserted.  An object with this id is created if it does not
  exist.