Run clang-modernize -use-nullptr over src/extensions/.

extensions/renderer/object_backed_native_handler.cc

Index: extensions/renderer/object_backed_native_handler.cc
diff --git a/extensions/renderer/object_backed_native_handler.cc b/extensions/renderer/object_backed_native_handler.cc
index 0c75ea0e82160d0224bb78de6363d2fc14e7fa04..4ed8f1bb034dc3b5ec28fa3428fc0b5474366b59 100644
--- a/extensions/renderer/object_backed_native_handler.cc
+++ b/extensions/renderer/object_backed_native_handler.cc
@@ -90,7 +90,7 @@ void ObjectBackedNativeHandler::Invalidate() {
   }
   router_data_.Clear();
   object_template_.reset();
-  context_ = NULL;
+  context_ = nullptr;
   NativeHandler::Invalidate();
 }