[Sync] Make GetFirstChildId return a flag indicating success

chrome/browser/sync/engine/apply_updates_command_unittest.cc

Index: chrome/browser/sync/engine/apply_updates_command_unittest.cc
diff --git a/chrome/browser/sync/engine/apply_updates_command_unittest.cc b/chrome/browser/sync/engine/apply_updates_command_unittest.cc
index 7ea70c371bc1b4431b5c6e35e634990f240c37bb..852379137544a54142a6c7fe76cfdbf3c1968309 100644
--- a/chrome/browser/sync/engine/apply_updates_command_unittest.cc
+++ b/chrome/browser/sync/engine/apply_updates_command_unittest.cc
@@ -113,7 +113,9 @@ class ApplyUpdatesCommandTest : public SyncerCommandTest {
     ScopedDirLookup dir(syncdb()->manager(), syncdb()->name());
     ASSERT_TRUE(dir.good());
     WriteTransaction trans(FROM_HERE, UNITTEST, dir);
-    Id predecessor_id = dir->GetLastChildId(&trans, parent_id);
+    Id predecessor_id;
+    ASSERT_TRUE(
+        dir->GetLastChildIdForTest(&trans, parent_id, &predecessor_id));
     MutableEntry entry(&trans, syncable::CREATE, parent_id, name);
     ASSERT_TRUE(entry.good());
     entry.Put(syncable::ID, item_id);