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

components/sync/syncable/entry_kernel.h

Index: components/sync/syncable/entry_kernel.h
diff --git a/components/sync/syncable/entry_kernel.h b/components/sync/syncable/entry_kernel.h
index d231c30081068b11cc96ed94ede0989e5f093f41..77495e144804a9b614c111d11011be05584f96bf 100644
--- a/components/sync/syncable/entry_kernel.h
+++ b/components/sync/syncable/entry_kernel.h
@@ -140,7 +140,7 @@ enum {
 };
 
 // From looking at the sqlite3 docs, it's not directly stated, but it
-// seems the overhead for storing a NULL blob is very small.
+// seems the overhead for storing a null blob is very small.
 enum ProtoField {
   SPECIFICS = PROTO_FIELDS_BEGIN,
   SERVER_SPECIFICS,
@@ -373,7 +373,7 @@ struct EntryKernel {
   // Dumps all kernel info into a DictionaryValue and returns it.
   // Transfers ownership of the DictionaryValue to the caller.
   // Note: |cryptographer| is an optional parameter for use in decrypting
-  // encrypted specifics. If it is NULL or the specifics are not decryptsble,
+  // encrypted specifics. If it is null or the specifics are not decryptsble,
   // they will be serialized as empty proto's.
   base::DictionaryValue* ToValue(Cryptographer* cryptographer) const;