Add MathML CSS fallback

assets/javascripts/vendor/mathml.js

@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. 
+ * Adapted from: https://github.com/fred-wang/mathml.css */
+/*jslint browser: true*/
+
+(function () {
+    "use strict";
+    window.addEventListener("load", function () {
+        var box, div, link, namespaceURI;
+        // First check whether the page contains any <math> element.
+        namespaceURI = "http://www.w3.org/1998/Math/MathML";
+        // Create a div to test mspace, using Kuma's "offscreen" CSS
+        document.body.insertAdjacentHTML("afterbegin", "<div style='border: 0; clip: rect(0 0 0 0); height: 1px; margin: -1px; overflow: hidden; padding: 0; position: absolute; width: 1px;'><math xmlns='" + namespaceURI + "'><mspace height='23px' width='77px'></mspace></math></div>");
+        div = document.body.firstChild;
+        box = div.firstChild.firstChild.getBoundingClientRect();
+        document.body.removeChild(div);
+        if (Math.abs(box.height - 23) > 1  || Math.abs(box.width - 77) > 1) {
+            // Insert the mathml.css stylesheet.
+            link = document.createElement("link");
+            link.href = "http://fred-wang.github.io/mathml.css/mathml.css";
+            link.rel = "stylesheet";
+            document.head.appendChild(link);
+        }
+    });
+}());