[Sync] Fix flakiness from Sessions refactor

chrome/browser/sync/sessions/sessions_sync_manager_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sync_sessions/sessions_sync_manager.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 2033 matching lines @@
   // Verify second tab.
   const sync_pb::SessionTab& tab2_1 =
       out[6].sync_data().GetSpecifics().session().tab();
   ASSERT_EQ(1, tab2_1.navigation_size());
   EXPECT_EQ(bar1.spec(), tab2_1.navigation(0).virtual_url());
   const sync_pb::SessionTab& tab2_2 =
       out[8].sync_data().GetSpecifics().session().tab();
   ASSERT_EQ(2, tab2_2.navigation_size());
   EXPECT_EQ(bar1.spec(), tab2_2.navigation(0).virtual_url());
   EXPECT_EQ(bar2.spec(), tab2_2.navigation(1).virtual_url());
+
+  // Verify tab delegates have Sync ids.
+  std::set<const SyncedWindowDelegate*> window_delegates =
+      get_synced_window_getter()->GetSyncedWindowDelegates();
+  // Sync ids are in reverse order because tabs are inserted at the beginning
+  // of the tab list.
+  EXPECT_EQ(1, (*window_delegates.begin())->GetTabAt(0)->GetSyncId());
+  EXPECT_EQ(0, (*window_delegates.begin())->GetTabAt(1)->GetSyncId());
 }
 
 // Check that if a tab becomes uninteresting (for example no syncable URLs),
 // we correctly remove it from the header node.
 TEST_F(SessionsSyncManagerTest, TabBecomesUninteresting) {
   syncer::SyncChangeList out;
   // Init with no local data, relies on MergeLocalSessionNoTabs.
   InitWithSyncDataTakeOutput(syncer::SyncDataList(), &out);
   ASSERT_FALSE(manager()->current_machine_tag().empty());
   ASSERT_EQ(2U, out.size());
@@ skipping 90 matching lines @@
   EXPECT_TRUE(out[3].IsValid());
   EXPECT_EQ(SyncChange::ACTION_UPDATE, out[3].change_type());
   const SyncData data_2(out[3].sync_data());
   EXPECT_EQ(manager()->current_machine_tag(),
             syncer::SyncDataLocal(data_2).GetTag());
   const sync_pb::SessionSpecifics& specifics2(data_2.GetSpecifics().session());
   EXPECT_EQ(manager()->current_machine_tag(), specifics2.session_tag());
   EXPECT_TRUE(specifics2.has_header());
   const sync_pb::SessionHeader& header_s2 = specifics2.header();
   EXPECT_EQ(1, header_s2.window_size());
+
+  // Verify tab delegates have Sync ids.
+  std::set<const SyncedWindowDelegate*> window_delegates =
+      get_synced_window_getter()->GetSyncedWindowDelegates();
+  // Sync ids are in same order as tabs because the association happens after
+  // the tabs are opened (and therefore iterates through same order).
+  EXPECT_EQ(0, (*window_delegates.begin())->GetTabAt(0)->GetSyncId());
+  EXPECT_EQ(1, (*window_delegates.begin())->GetTabAt(1)->GetSyncId());
 }
 
 TEST_F(SessionsSyncManagerTest, ForeignSessionModifiedTime) {
   syncer::SyncDataList foreign_data;
   base::Time newest_time = base::Time::Now() - base::TimeDelta::FromDays(1);
   base::Time middle_time = base::Time::Now() - base::TimeDelta::FromDays(2);
   base::Time oldest_time = base::Time::Now() - base::TimeDelta::FromDays(3);
 
   {
     std::string session_tag = "tag1";
@@ skipping 517 matching lines @@
   base::Time last_time;
   for (size_t i = 0; i < tabs.size(); ++i) {
     base::Time this_time = tabs[i]->timestamp;
     if (i > 0)
       ASSERT_GE(last_time, this_time);
     last_time = tabs[i]->timestamp;
   }
 }
 
 }  // namespace sync_sessions