Implement new invalidations ack tracking system

sync/notifier/object_id_invalidation_map.cc

Index: sync/notifier/object_id_invalidation_map.cc
diff --git a/sync/notifier/object_id_invalidation_map.cc b/sync/notifier/object_id_invalidation_map.cc
index e1f584d0e4eb812b329dc2cb33e48cfe6dde3da4..1082eaa29be1f85f971e53955bd15a8524e84eb2 100644
--- a/sync/notifier/object_id_invalidation_map.cc
+++ b/sync/notifier/object_id_invalidation_map.cc
@@ -64,6 +64,15 @@ void ObjectIdInvalidationMap::GetAllInvalidations(
     out->insert(out->begin(), it->second.begin(), it->second.end());
   }
 }
+void ObjectIdInvalidationMap::AcknowledgeAll() const {
+  for (IdToListMap::const_iterator it1 = map_.begin();
+       it1 != map_.end(); ++it1) {
+    for (SingleObjectInvalidationSet::const_iterator it2 = it1->second.begin();
+         it2 != it1->second.end(); ++it2) {
+      it2->Acknowledge();
+    }
+  }
+}
 
 bool ObjectIdInvalidationMap::operator==(
     const ObjectIdInvalidationMap& other) const {