message: (hopefully) fix theming on Chrome
  Jump through some hoops to make Chrome behave sensibly on non-default themes.
diff: @@ -598,20 +598,32 @@ module.exports = React.createClass({
  theme = 'light';
  }
  + // look for the stylesheet elements.
  + // styleElements is a map from style name to HTMLLinkElement.
  + var styleElements = Object.create(null);
  var i, a;
  for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) {
  var href = a.getAttribute("href");
  + // shouldn't we be using the 'title' tag rather than the href?
  var match = href.match(/^bundles\/.*\/theme-(.*)\.css$/);
  if (match) {
  - if (match[1] === theme) {
  - a.disabled = false;
  - }
  - else {
  - a.disabled = true;
  + styleElements[match[1]] = a;
  }
  }
  +
  + if (!(theme in styleElements)) {
  + throw new Error("Unknown theme " + theme);
  }
  + // disable all of them first, then enable the one we want. Chrome only
  + // bothers to do an update on a true->false transition, so this ensures
  + // that we get exactly one update, at the right time.
  +
  + Object.values(styleElements).forEach((a) => {
  + a.disabled = true;
  + });
  + styleElements[theme].disabled = false;
  +
  if (theme === 'dark') {
  // abuse the tinter to change all the SVG's #fff to #2d2d2d
  // XXX: obviously this shouldn't be hardcoded here.
  