Fix SHIFT+TAB order on GAIA login screens

chrome/browser/resources/gaia_auth_host/authenticator.js

Index: chrome/browser/resources/gaia_auth_host/authenticator.js
diff --git a/chrome/browser/resources/gaia_auth_host/authenticator.js b/chrome/browser/resources/gaia_auth_host/authenticator.js
index c5a1da21c949682e3785a6a25cde77f4c79d2104..870b368258f4f6e5aa5bad23b0bbf15c8259df68 100644
--- a/chrome/browser/resources/gaia_auth_host/authenticator.js
+++ b/chrome/browser/resources/gaia_auth_host/authenticator.js
@@ -185,6 +185,7 @@ cr.define('cr.login', function() {
    * @param {Object} data Parameters for the authorization flow.
    */
   Authenticator.prototype.load = function(authMode, data) {
+    this.authMode = authMode;
     this.clearCredentials_();
     this.loaded_ = false;
     this.idpOrigin_ = data.gaiaUrl || IDP_ORIGIN;
@@ -322,7 +323,8 @@ cr.define('cr.login', function() {
    * @private
    */
   Authenticator.prototype.onFocus_ = function(e) {
-    this.webview_.focus();
+    if (this.authMode == AuthMode.DESKTOP)
+      this.webview_.focus();
   };
 
   /**