Replace base::NullableString16(bool) usage with default constructor.

content/browser/web_contents/web_drag_dest_gtk.cc

Index: content/browser/web_contents/web_drag_dest_gtk.cc
diff --git a/content/browser/web_contents/web_drag_dest_gtk.cc b/content/browser/web_contents/web_drag_dest_gtk.cc
index 1e57716d934f89e579800551c803d70bcc5a1c2b..c745d31b12ba16559967ba63527ec60eb7f549c8 100644
--- a/content/browser/web_contents/web_drag_dest_gtk.cc
+++ b/content/browser/web_contents/web_drag_dest_gtk.cc
@@ -209,7 +209,7 @@ void WebDragDestGtk::OnDragDataReceived(
             // This is a hack. Some file managers also populate text/plain with
             // a file URL when dragging files, so we clear it to avoid exposing
             // it to the web content.
-            drop_data_->text = base::NullableString16(true);
+            drop_data_->text = base::NullableString16();
           } else if (!drop_data_->url.is_valid()) {
             // Also set the first non-file URL as the URL content for the drop.
             drop_data_->url = url;