pinned checkbox is checked by default

frontend-js/src/main/js/gui/CommentDialog.js

@@ -85,6 +85,8 @@ CommentDialog.prototype._createGui = function() {
   pinnedLabel.innerHTML = "Pinned";
   var pinnedCheckbox = document.createElement('input');
   pinnedCheckbox.type = "checkbox";
+  pinnedCheckbox.checked = "checked";
+
 
   table.appendChild(createRow([ pinnedLabel, pinnedCheckbox ]));
   this.setPinnedCheckbox(pinnedCheckbox);