LibWeb: Implement Navigator.doNotTrack

Author: https://github.com/jamierocks
Commit: 61e616c974
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/373
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibWeb/HTML/Navigator.cpp

@@ -13,6 +13,7 @@
 #include <LibWeb/HTML/Navigator.h>
 #include <LibWeb/HTML/Scripting/Environments.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/Loader/ResourceLoader.h>
 #include <LibWeb/Page/Page.h>
 
 namespace Web::HTML {
@@ -100,4 +101,16 @@ WebIDL::Long Navigator::max_touch_points()
     return 0;
 }
 
+// https://www.w3.org/TR/tracking-dnt/#dom-navigator-donottrack
+Optional<FlyString> Navigator::do_not_track() const
+{
+    // The value is null if no DNT header field would be sent (e.g., because a tracking preference is not
+    // enabled and no user-granted exception is applicable); otherwise, the value is a string beginning with
+    // "0" or "1", possibly followed by DNT-extension characters.
+    if (ResourceLoader::the().enable_do_not_track())
+        return "1"_fly_string;
+
+    return {};
+}
+
 }