Mojo: NULL -> nullptr in mojo/public/cpp/bindings and also for the bindings generator.

mojo/public/cpp/bindings/message_filter.h

Index: mojo/public/cpp/bindings/message_filter.h
diff --git a/mojo/public/cpp/bindings/message_filter.h b/mojo/public/cpp/bindings/message_filter.h
index 5c3dcda18e561c4b65250565ba24011f2a297f89..f4faafb7d741a4f360c8b5d1352eabb0d1b0ed97 100644
--- a/mojo/public/cpp/bindings/message_filter.h
+++ b/mojo/public/cpp/bindings/message_filter.h
@@ -17,7 +17,7 @@ class MessageFilter : public MessageReceiver {
  public:
   // Doesn't take ownership of |sink|. Therefore |sink| has to stay alive while
   // this object is alive.
-  explicit MessageFilter(MessageReceiver* sink = NULL);
+  explicit MessageFilter(MessageReceiver* sink = nullptr);
   virtual ~MessageFilter();
 
   void set_sink(MessageReceiver* sink) { sink_ = sink; }
@@ -29,7 +29,7 @@ class MessageFilter : public MessageReceiver {
 // A trivial filter that simply forwards every message it receives to |sink_|.
 class PassThroughFilter : public MessageFilter {
  public:
-  explicit PassThroughFilter(MessageReceiver* sink = NULL);
+  explicit PassThroughFilter(MessageReceiver* sink = nullptr);
 
   virtual bool Accept(Message* message) override;
 };