MD History: add sign in promo in synced tabs when user isn't logged in

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 dfce76a312755819d2d823a102ffdbe20e3339f2..353d81d37126a1c7bb420e1ede27b70723841090 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
@@ -173,6 +173,75 @@ cr.define('md_history.history_synced_tabs_test', function() {
         });
       });
 
+      test('show sign in promo', function() {
+        updateSignInState(false);
+        return flush()
+            .then(function() {

[tsergeant, 2016/06/21 04:33:51]

Put flush and then on the same line, then indent by two spaces.

return flush().then(function() {
  blah()
  blah()
}

[lshang, 2016/06/21 05:40:00]

Done.

+              assertFalse(element.$['sign-in-guide'].hidden);
+              updateSignInState(true);
+              return flush();
+            })
+            .then(function() {
+              assertTrue(element.$['sign-in-guide'].hidden);
+            });
+      });
+
+      test('no synced tabs message', function() {
+        // When user is not logged in, there is no synced tabs.
+        element.signInState_ = false;
+        element.syncedDevices_ = [];
+
+        return flush().then(function() {
+          assertTrue(element.$['no-synced-tabs'].hidden);
+
+          var cards = getCards();
+          assertEquals(0, cards.length);
+
+          updateSignInState(true);
+
+          return flush();
+        }).then(function() {
+          // When user signs in, first show loading message.
+          assertFalse(element.$['no-synced-tabs'].hidden);
+          assertEquals(
+              '\n      Loading...\n    ',

[tsergeant, 2016/06/21 04:33:51]

Checking the string like this is quite means that this test won't work in
non-English, and it will break if the spacing changes or the string changes.

A better approach would be to use indexOf and loadTimeData:

var loading = loadTimeData.getString('loading');
assertNotEquals(-1, element.$['no-synced-tabs'].textContent.indexOf(loading))

[lshang, 2016/06/21 05:40:00]

Done.

+              element.$['no-synced-tabs'].textContent);
+
+          var sessionList = [];
+          setForeignSessions(sessionList, true);
+          return flush();
+        }).then(function() {
+          cards = getCards();
+          assertEquals(0, cards.length);
+          // If no synced tabs are fetched, show 'no synced tabs'.
+          assertFalse(element.$['no-synced-tabs'].hidden);
+          assertEquals(
+              '\n      No synced tabs\n    ',
+              element.$['no-synced-tabs'].textContent);
+
+          var sessionList = [
+            createSession(
+                'Nexus 5',
+                [createWindow(['http://www.google.com', 'http://example.com'])]
+            )
+          ];
+          setForeignSessions(sessionList, true);
+
+          return flush();
+        }).then(function() {
+          cards = getCards();
+          assertEquals(1, cards.length);
+          // If there are any synced tabs, hide the 'no synced tab' message.
+          assertTrue(element.$['no-synced-tabs'].hidden);
+
+          updateSignInState(false);
+          return flush();
+        }).then(function() {
+          // When user signs out, don't show the message.
+          assertTrue(element.$['no-synced-tabs'].hidden);
+        });
+      });
+
       teardown(function() {
         element.syncedDevices = [];
         element.searchedTerm = '';