Mojo: NULL -> nullptr in mojo/system and mojo/embedder.

mojo/embedder/simple_platform_shared_buffer_win.cc

Index: mojo/embedder/simple_platform_shared_buffer_win.cc
diff --git a/mojo/embedder/simple_platform_shared_buffer_win.cc b/mojo/embedder/simple_platform_shared_buffer_win.cc
index d2caa2e94dfb8a0944aa1c1ad87b479e9f9ad4c5..1167ac5fa0616b5d5296261de38af65fe79b04ae 100644
--- a/mojo/embedder/simple_platform_shared_buffer_win.cc
+++ b/mojo/embedder/simple_platform_shared_buffer_win.cc
@@ -34,11 +34,11 @@ bool SimplePlatformSharedBuffer::Init() {
   // multiple of 64 KB). This may cause problems with NaCl. Cross this bridge
   // when we get there. crbug.com/210609
   handle_.reset(PlatformHandle(CreateFileMapping(INVALID_HANDLE_VALUE,
-                                                 NULL,
+                                                 nullptr,
                                                  PAGE_READWRITE,
                                                  0,
                                                  static_cast<DWORD>(num_bytes_),
-                                                 NULL)));
+                                                 nullptr)));
   if (!handle_.is_valid()) {
     PLOG(ERROR) << "CreateFileMapping";
     return false;