Fix cpplint whitespace/braces issues

Change-Id: Ide80939faf8e8690d8842dde8133902ac725ed1a
diff --git a/runtime/base/mutex.cc b/runtime/base/mutex.cc
index fbec826..bb4b5c5 100644
--- a/runtime/base/mutex.cc
+++ b/runtime/base/mutex.cc
@@ -465,7 +465,7 @@
 #if ART_USE_FUTEXES
     , state_(0), exclusive_owner_(0), num_pending_readers_(0), num_pending_writers_(0)
 #endif
-{
+{ // NOLINT(whitespace/braces)
 #if !ART_USE_FUTEXES
   CHECK_MUTEX_CALL(pthread_rwlock_init, (&rwlock_, NULL));
 #endif