Migrate invalidator client IDs out of sync

sync/tools/null_invalidation_state_tracker.cc

Index: sync/tools/null_invalidation_state_tracker.cc
diff --git a/sync/tools/null_invalidation_state_tracker.cc b/sync/tools/null_invalidation_state_tracker.cc
index 5eb5f788cb2fd290183f272b942468e2ac3da9bd..084630c99f14ae0155ee67d5b3740edbb5da5a5d 100644
--- a/sync/tools/null_invalidation_state_tracker.cc
+++ b/sync/tools/null_invalidation_state_tracker.cc
@@ -37,6 +37,15 @@ void NullInvalidationStateTracker::Forget(const ObjectIdSet& ids) {
   }
 }
 
+void NullInvalidationStateTracker::SetInvalidatorClientId(
+    const std::string& data) {
+  LOG(INFO) << "Setting invalidator client ID to: " << data;
+}
+
+std::string NullInvalidationStateTracker::GetInvalidatorClientId() const {
+  return std::string();
+}
+
 std::string NullInvalidationStateTracker::GetBootstrapData() const {
   return std::string();
 }