Update sync/ to use WeakPtr<T>::get() instead of implicit "operator T*"

sync/notifier/invalidator_factory.cc

Index: sync/notifier/invalidator_factory.cc
diff --git a/sync/notifier/invalidator_factory.cc b/sync/notifier/invalidator_factory.cc
index 6b6992488793c89663a851c4da99343cd5887154..f359ce8365143f61080b2bae20ef74858b0f5d4f 100644
--- a/sync/notifier/invalidator_factory.cc
+++ b/sync/notifier/invalidator_factory.cc
@@ -59,7 +59,7 @@ InvalidatorFactory::InvalidatorFactory(
         invalidation_state_tracker)
     : notifier_options_(notifier_options),
       client_info_(client_info) {
-  if (!invalidation_state_tracker) {
+  if (!invalidation_state_tracker.get()) {
     return;
   }