Update mojo sdk to rev f6c8ec07c01deebc13178d516225fd12695c3dc2

mojo/public/cpp/utility/lib/thread_local_posix.cc

Index: mojo/public/cpp/utility/lib/thread_local_posix.cc
diff --git a/mojo/public/cpp/utility/lib/thread_local_posix.cc b/mojo/public/cpp/utility/lib/thread_local_posix.cc
index b33dfc61297cae792f5865ae28a1d0adf0b4b1ac..ea7343e5e69aca5d35a5c5d3604758a85b2200ac 100644
--- a/mojo/public/cpp/utility/lib/thread_local_posix.cc
+++ b/mojo/public/cpp/utility/lib/thread_local_posix.cc
@@ -11,7 +11,7 @@ namespace internal {
 
 // static
 void ThreadLocalPlatform::AllocateSlot(SlotType* slot) {
-  if (pthread_key_create(slot, NULL) != 0) {
+  if (pthread_key_create(slot, nullptr) != 0) {
     assert(false);
   }
 }