code: function loadFont (fontFace, callback) {
    var defaultNode;
    var testNode;
    var checkFont;
  
    // See if we've previously loaded it.
    if (_loadedFonts[fontFace.id]) {
      return callback(null);
    }
  
    // See if we've previously failed to load it.
    if (_failedFonts[fontFace.id]) {
      return callback(_failedFonts[fontFace.id]);
    }
  
    // System font: assume already loaded.
    if (!fontFace.url) {
      return callback(null);
    }
  
    // Font load is already in progress:
    if (_pendingFonts[fontFace.id]) {
      _pendingFonts[fontFace.id].callbacks.push(callback);
      return;
    }
  
    // Create the test <span>'s for measuring.
    defaultNode = createTestNode('Helvetica', fontFace.attributes);
    testNode = createTestNode(fontFace.family, fontFace.attributes);
    document.body.appendChild(testNode);
    document.body.appendChild(defaultNode);
  
    _pendingFonts[fontFace.id] = {
      startTime: Date.now(),
      defaultNode: defaultNode,
      testNode: testNode,
      callbacks: [callback]
    };
  
    // Font watcher
    checkFont = function () {
      var currWidth = testNode.getBoundingClientRect().width;
      var defaultWidth = defaultNode.getBoundingClientRect().width;
      var loaded = currWidth !== defaultWidth;
  
      if (loaded) {
        handleFontLoad(fontFace, null);
      } else {
        // Timeout?
        if (Date.now() - _pendingFonts[fontFace.id].startTime >= kFontLoadTimeout) {
          handleFontLoad(fontFace, true);
        } else {
          requestAnimationFrame(checkFont);
        }
      }
    };
  
    // Start watching
    checkFont();
  }
docs: Load a remote font and execute a callback.
  @param {FontFace} fontFace The font to Load
  @param {Function} callback Function executed upon font Load