Avoid Syntax Highlighting fullscreen augmentation on regular textareas

/* Before going into fullscreen editing, record the element's original dimensions. */
document.observe('xwiki:fullscreen:enter', function(event) {
  var codeMirror = getCodeMirrorFromFullScreenEvent(event);
  var editorDiv = codeMirror.getWrapperElement();
  ...

/* Fullscreen left by pressing the bottom button. */
document.observe('xwiki:fullscreen:exited', function(event) {
var codeMirror = getCodeMirrorFromFullScreenEvent(event);
toggleFullscreenEditing(codeMirror, false);
});