[Web] Add u2f api from bitwardens repository to skip u2f when it is browser-provided

data/web/js/u2f-api.js

@@ -4,17 +4,41 @@
 //license that can be found in the LICENSE file or at
 //https://developers.google.com/open-source/licenses/bsd
 
+// ref: https://github.com/google/u2f-ref-code/blob/master/u2f-gae-demo/war/js/u2f-api.js
+
 /**
  * @fileoverview The U2F api.
  */
 'use strict';
 
+/**
+ * Modification:
+ * Wrap implementation so that we can exit if window.u2f is already supplied by the browser (see below).
+ */
+(function (root) {
+    /**
+     * Modification:
+     * Only continue load this library if window.u2f is not already supplied by the browser.
+     */
+    var isFirefox = navigator.userAgent.indexOf('Firefox') !== -1 || navigator.userAgent.indexOf('Gecko/') !== -1;
+    var browserImplementsU2f = !!((typeof root.u2f !== 'undefined') && root.u2f.register);
+
+    if (isFirefox && browserImplementsU2f) {
+        root.u2f.isSupported = true;
+        return;
+    }
 
     /**
      * Namespace for the U2F api.
      * @type {Object}
      */
-var u2f = u2f || {};
+    var u2f = root.u2f || {};
+
+    /**
+     * Modification:
+     * Check if browser supports U2F API before this wrapper was added.
+     */
+    u2f.isSupported = !!(((typeof u2f !== 'undefined') && u2f.register) || ((typeof chrome !== 'undefined') && chrome.runtime));
 
     /**
      * FIDO U2F Javascript API Version
@@ -746,3 +770,10 @@ u2f.getApiVersion = function(callback, opt_timeoutSeconds) {
             port.postMessage(req);
         });
     };
+
+    /**
+     * Modification:
+     * Assign u2f back to window (root) scope.
+     */
+    root.u2f = u2f;
+}(this));