android.moparisthebest.org/source/javascripts/libs/ios-viewport-scaling-bug-fix.js

// https://gist.github.com/901295
// By @mathias, @cheeaun and @jdalton

(function(doc) {
  var addEvent = 'addEventListener',
  type = 'gesturestart',
  qsa = 'querySelectorAll',
  scales = [1, 1],
  meta = qsa in doc ? doc[qsa]('meta[name=viewport]') : [];
  function fix() {
    meta.content = 'width=device-width,minimum-scale=' + scales[0] + ',maximum-scale=' + scales[1];
    doc.removeEventListener(type, fix, true);
  }
  if ((meta = meta[meta.length - 1]) && addEvent in doc) {
    fix();
    scales = [.25, 1.6];
    doc[addEvent](type, fix, true);
  }
}(document));