MD History: Hide sign in guide in guest mode

chrome/test/data/webui/md_history/history_synced_tabs_test.js

Index: chrome/test/data/webui/md_history/history_synced_tabs_test.js
diff --git a/chrome/test/data/webui/md_history/history_synced_tabs_test.js b/chrome/test/data/webui/md_history/history_synced_tabs_test.js
index 60e80096678417461c72ba1066046b7cfe23230f..5c46fb55e38271428da438e385e0e438eda7bdfd 100644
--- a/chrome/test/data/webui/md_history/history_synced_tabs_test.js
+++ b/chrome/test/data/webui/md_history/history_synced_tabs_test.js
@@ -253,9 +253,17 @@ cr.define('md_history.history_synced_tabs_test', function() {
         });
       });
 
+      test('hide sign in promo in guest mode', function() {
+        element.guestSession_ = true;
+        return flush().then(function() {
+          assertTrue(element.$['sign-in-guide'].hidden);
+        });
+      });
+
       teardown(function() {
         element.syncedDevices = [];
         element.searchTerm = '';
+        element.guestSession_ = false;
       });
     });
   }