code: function writeElements(res, elements) {
  
  	// Pick up where we left off.
  	var start = RLS().nextElement||(RLS().nextElement=0);
  
  	for (var i = start; i < elements.length; RLS().nextElement = ++i){
  
  		// If we haven't rendered the next element yet, we're done.
  		if (elements[i] === ELEMENT_PENDING) break;
  
  		// Got one!
  		writeElement(res, elements[i], i);
  
  		// Free for GC.
  		elements[i] = ELEMENT_ALREADY_WRITTEN;
  
  		if (PageUtil.PageConfig.get('isFragment')) continue;
  
  		if (RLS().haveBootstrapped) {
  
  			// We've already bootstrapped, so we can immediately tell the
  			// client controller to wake the new element we just sent.
  			wakeElementRange(res, i, i);
  		} else if (i === elements.length - 1) {
  
  			// Page didn't emit `<TheFold/>`.  Now we're done.
  			// This wakes everything up through `i`.
  			bootstrapClient(res, i);
  		}
  	}
  
  	// It may be a while before we render the next element, so if we just
  	// wrote anything let's send it down right away.
  	if (i !== start) flushRes(res);
  }
docs: Write as many elements out in a row as possible and then flush output. We render elements as their data becomes available, so they might fill in out-of-order.