Implement new invalidations ack tracking system

sync/notifier/fake_invalidator.cc

Index: sync/notifier/fake_invalidator.cc
diff --git a/sync/notifier/fake_invalidator.cc b/sync/notifier/fake_invalidator.cc
index 0b217f79e1e309753a0c087a6b6e4b2aa95f75cd..3e1ce32250be15f11ae74ad286add28943317507 100644
--- a/sync/notifier/fake_invalidator.cc
+++ b/sync/notifier/fake_invalidator.cc
@@ -4,6 +4,8 @@
 
 #include "sync/notifier/fake_invalidator.h"
 
+#include "sync/notifier/object_id_invalidation_map.h"
+
 namespace syncer {
 
 FakeInvalidator::FakeInvalidator() {}
@@ -49,11 +51,6 @@ void FakeInvalidator::UnregisterHandler(InvalidationHandler* handler) {
   registrar_.UnregisterHandler(handler);
 }
 
-void FakeInvalidator::Acknowledge(const invalidation::ObjectId& id,
-                                  const AckHandle& ack_handle) {
-  // Do nothing.
-}
-
 InvalidatorState FakeInvalidator::GetInvalidatorState() const {
   return registrar_.GetInvalidatorState();
 }