Update IDE file mirror service (ce utils)

**Notes:**
This module is a client to the webide-file-sync service.
https://gitlab.com/gitlab-org/webide-file-sync

app/assets/javascripts/lib/utils/url_utility.js

+import { join as joinPaths } from 'path';
+
 // Returns an array containing the value(s) of the
 // of the key passed as an argument
 export function getParameterValues(sParam) {
@@ -157,4 +159,12 @@ export function isSafeURL(url) {
   }
 }
 
-export { join as joinPaths } from 'path';
+export function getWebSocketProtocol() {
+  return window.location.protocol.replace('http', 'ws');
+}
+
+export function getWebSocketUrl(path) {
+  return `${getWebSocketProtocol()}//${joinPaths(window.location.host, path)}`;
+}
+
+export { joinPaths };

spec/frontend/lib/utils/url_utility_spec.js

 import * as urlUtils from '~/lib/utils/url_utility';
 
+const setWindowLocation = value => {
+  Object.defineProperty(window, 'location', {
+    writable: true,
+    value,
+  });
+};
+
 describe('URL utility', () => {
   describe('webIDEUrl', () => {
     afterEach(() => {
@@ -110,12 +117,9 @@ describe('URL utility', () => {
 
   describe('getBaseURL', () => {
     beforeEach(() => {
-      global.window = Object.create(window);
-      Object.defineProperty(window, 'location', {
-        value: {
-          host: 'gitlab.com',
+      setWindowLocation({
         protocol: 'https:',
-        },
+        host: 'gitlab.com',
       });
     });
 
@@ -191,4 +195,32 @@ describe('URL utility', () => {
       });
     });
   });
+
+  describe('getWebSocketProtocol', () => {
+    it.each`
+      protocol    | expectation
+      ${'http:'}  | ${'ws:'}
+      ${'https:'} | ${'wss:'}
+    `('returns "$expectation" with "$protocol" protocol', ({ protocol, expectation }) => {
+      setWindowLocation({
+        protocol,
+        host: 'example.com',
+      });
+
+      expect(urlUtils.getWebSocketProtocol()).toEqual(expectation);
+    });
+  });
+
+  describe('getWebSocketUrl', () => {
+    it('joins location host to path', () => {
+      setWindowLocation({
+        protocol: 'http:',
+        host: 'example.com',
+      });
+
+      const path = '/lorem/ipsum?a=bc';
+
+      expect(urlUtils.getWebSocketUrl(path)).toEqual('ws://example.com/lorem/ipsum?a=bc');
+    });
+  });
 });