function jscoverage_initTabControl() {
  var tabs = document.getElementById('tabs');
  var i;
  var child;
  var tabNum = 0;
  for (i = 0; i < tabs.childNodes.length; i++) {
    child = tabs.childNodes.item(i);
    if (child.nodeType === 1) {
      if (child.className !== 'disabled') {
        child.onclick = jscoverage_tab_click;
      }
      tabNum++;
    }
  }
  jscoverage_selectTab(0);
}
Initializes the tab control.  This function must be called when the document is
loaded.