Indicates visually that a lengthy operation has begun.  The progress bar is
displayed, and the cursor is changed to busy (on browsers which support this).
function jscoverage_beginLengthyOperation() {
  jscoverage_inLengthyOperation = true;

  var progressBar = document.getElementById('progressBar');
  progressBar.style.visibility = 'visible';
  ProgressBar.setPercentage(progressBar, 0);
  var progressLabel = document.getElementById('progressLabel');
  progressLabel.style.visibility = 'visible';

  /* blacklist buggy browsers */
//#JSCOVERAGE_IF
  if (! /Opera|WebKit/.test(navigator.userAgent)) {
    /*
    Change the cursor style of each element.  Note that changing the class of the
    element (to one with a busy cursor) is buggy in IE.
    */
    var tabs = document.getElementById('tabs').getElementsByTagName('div');
    var i;
    for (i = 0; i < tabs.length; i++) {
      tabs.item(i).style.cursor = 'wait';
    }
  }
}