[C++11 Allowed Features] Declares a type-safe null pointer converting from NULL to nullptr in src/…

cc/resources/task_graph_runner.cc

Index: cc/resources/task_graph_runner.cc
diff --git a/cc/resources/task_graph_runner.cc b/cc/resources/task_graph_runner.cc
index bcbc0dd351c03bbd15153323dcf53b68bca469e2..32bb325616e18b938636afb0c51dfcc55a4fca3d 100644
--- a/cc/resources/task_graph_runner.cc
+++ b/cc/resources/task_graph_runner.cc
@@ -20,7 +20,7 @@ class DependentIterator {
       : graph_(graph),
         task_(task),
         current_index_(static_cast<size_t>(-1)),
-        current_node_(NULL) {
+        current_node_(nullptr) {
     ++(*this);
   }