This tests aborting font files from Google web fonts. This works as expected.

Test Google Fonts

var page = require('webpage').create();

// Block fonts
var abort_content_types = [
  "application/x-font-woff",
  "font/woff",
  "font/opentype",
];

// Default user agent won't work with TypeKit
page.settings.userAgent = 'Mozilla/5.0 (Windows NT 6.0; WOW64) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.75 Safari/535.7';

page.onResourceRequested = function(resourceData, res) {
  if (abort_content_types.indexOf(resourceData["contentType"]) != -1) {
    console.log("Found contentType we should abort = " + resourceData["contentType"]);
    res.abort();
  }
};

page.onResourceReceived = function(res) {
  if (abort_content_types.indexOf(res["contentType"]) != -1) {
    console.log("ERROR: Should have aborted content, but received it = " + res["contentType"]);
  }
}

page.open('https://developers.google.com/fonts/docs/getting_started', function () {
  page.render('google.png');
  phantom.exit();
});