Rename random.{hexString => generateHexString}

Respond to CR feedback in
https://github.com/hypothesis/client/pull/476#discussion_r126539329

src/sidebar/oauth-auth.js

@@ -177,7 +177,7 @@ function auth($http, $window, flash, random, settings) {
   function login() {
     // Random state string used to check that auth messages came from the popup
     // window that we opened.
-    var state = random.hexString(16);
+    var state = random.generateHexString(16);
 
     // Promise which resolves or rejects when the user accepts or closes the
     // auth popup.

src/sidebar/test/oauth-auth-test.js

@@ -76,7 +76,7 @@ describe('sidebar.oauth-auth', function () {
     };
 
     fakeRandom = {
-      hexString: sinon.stub().returns('notrandom'),
+      generateHexString: sinon.stub().returns('notrandom'),
     };
 
     fakeSettings = {

src/sidebar/util/random.js

@@ -13,12 +13,12 @@ function byteToHex(val) {
  * @param {number} - An even-numbered length string to generate.
  * @return {string}
  */
-function hexString(len) {
+function generateHexString(len) {
   var bytes = new Uint8Array(len / 2);
   crypto.getRandomValues(bytes);
   return Array.from(bytes).map(byteToHex).join('');
 }
 
 module.exports = {
-  hexString,
+  generateHexString,
 };

src/sidebar/util/test/random-test.js

@@ -3,11 +3,11 @@
 var random = require('../random');
 
 describe('sidebar.util.random', () => {
-  describe('#hexString', () => {
+  describe('#generateHexString', () => {
     [2,4,8,16].forEach((len) => {
       it(`returns a ${len} digit hex string`, () => {
         var re = new RegExp(`^[0-9a-fA-F]{${len}}$`);
-        var str = random.hexString(len);
+        var str = random.generateHexString(len);
         assert.isTrue(re.test(str));
       });
     });