Allow the background page to get an OAuth token for apps v1.

BUG=

Review URL: https://codereview.chromium.org/687873003

Cr-Commit-Position: refs/heads/master@{#302172}
diff --git a/remoting/remoting_webapp_files.gypi b/remoting/remoting_webapp_files.gypi
index 179ca45fe..c0e3bfd 100644
--- a/remoting/remoting_webapp_files.gypi
+++ b/remoting/remoting_webapp_files.gypi
@@ -213,8 +213,11 @@
       'webapp/crd/js/it2me_host_facade.js',
       'webapp/crd/js/it2me_service.js',
       'webapp/crd/js/l10n.js',
+      'webapp/crd/js/oauth2.js',
+      'webapp/crd/js/oauth2_api.js',
       'webapp/crd/js/plugin_settings.js',
       'webapp/crd/js/typecheck.js',
+      'webapp/crd/js/xhr.js',
     ],
 
     # The JavaScript files required by wcs_sandbox.html.