[sync] Add regression test for TabContentsSyncedTabDelegate crash

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 8d6c727f4a0c393d0c469baf9863214cfc3522e7..19be315dc664a2ef694fad2cb7628f0c5aab75c6 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -3406,6 +3406,7 @@ test("unit_tests") {
     "../browser/ui/search_engines/keyword_editor_controller_unittest.cc",
     "../browser/ui/sync/profile_signin_confirmation_helper_unittest.cc",
     "../browser/ui/sync/sync_promo_ui_unittest.cc",
+    "../browser/ui/sync/tab_contents_synced_tab_delegate_unittest.cc",
     "../browser/ui/tests/ui_gfx_image_unittest.cc",
     "../browser/ui/tests/ui_gfx_image_unittest.mm",
     "../browser/ui/webui/browsing_history_handler_unittest.cc",
@@ -4814,6 +4815,7 @@ test("unit_tests") {
     sources -= [
       "../browser/ui/bookmarks/bookmark_ui_utils_desktop_unittest.cc",
       "../browser/ui/sync/sync_promo_ui_unittest.cc",
+      "../browser/ui/sync/tab_contents_synced_tab_delegate_unittest.cc",
     ]
   }
   if (!is_android && !is_chromeos) {