[Sync] Replacing NULL with nullptr in code and null in comments for components/sync/

components/sync/base/cryptographer.h

Index: components/sync/base/cryptographer.h
diff --git a/components/sync/base/cryptographer.h b/components/sync/base/cryptographer.h
index 1ef81d3ecda12526de9d1d19176c2b8dde5c3a1f..2ac9d55d4c75be5348f996f57787aebbf8a0d398 100644
--- a/components/sync/base/cryptographer.h
+++ b/components/sync/base/cryptographer.h
@@ -161,7 +161,7 @@ class Cryptographer {
   bool is_ready() const { return is_initialized() && !has_pending_keys(); }
 
   // Returns whether there is a pending set of keys that needs to be decrypted.
-  bool has_pending_keys() const { return NULL != pending_keys_.get(); }
+  bool has_pending_keys() const { return nullptr != pending_keys_.get(); }
 
   // Obtain a token that can be provided on construction to a future
   // Cryptographer instance to bootstrap itself.  Returns false if such a token