Replace NULL with nullptr or null in webrtc/base/.

webrtc/base/httpcommon-inl.h

Index: webrtc/base/httpcommon-inl.h
diff --git a/webrtc/base/httpcommon-inl.h b/webrtc/base/httpcommon-inl.h
index 75ede29f0f104540a862b5034a5b2cc44cb1602c..f29f0759985e4505c5a954a823bbd1259d0c38c9 100644
--- a/webrtc/base/httpcommon-inl.h
+++ b/webrtc/base/httpcommon-inl.h
@@ -53,7 +53,7 @@ void Url<CTYPE>::do_set_address(const CTYPE* val, size_t len) {
     host_.assign(val, colon - val);
     // Note: In every case, we're guaranteed that colon is followed by a null,
     // or non-numeric character.
-    port_ = static_cast<uint16_t>(::strtoul(colon + 1, NULL, 10));
+    port_ = static_cast<uint16_t>(::strtoul(colon + 1, nullptr, 10));
     // TODO: Consider checking for invalid data following port number.
   } else {
     host_.assign(val, len);