LibWeb: Stub out the HTMLMediaElement buffered attribute

This is needed by https://store.steampowered.com. For now, we return an
empty TimeRanges object.

Userland/Libraries/LibWeb/HTML/HTMLMediaElement.cpp

@@ -22,6 +22,7 @@
 #include <LibWeb/HTML/HTMLVideoElement.h>
 #include <LibWeb/HTML/PotentialCORSRequest.h>
 #include <LibWeb/HTML/Scripting/Environments.h>
+#include <LibWeb/HTML/TimeRanges.h>
 #include <LibWeb/HTML/TrackEvent.h>
 #include <LibWeb/HTML/VideoTrack.h>
 #include <LibWeb/HTML/VideoTrackList.h>
@@ -92,6 +93,19 @@ void HTMLMediaElement::parse_attribute(DeprecatedFlyString const& name, Deprecat
         load_element().release_value_but_fixme_should_propagate_errors();
 }
 
+// https://html.spec.whatwg.org/multipage/media.html#dom-media-buffered
+WebIDL::ExceptionOr<JS::NonnullGCPtr<TimeRanges>> HTMLMediaElement::buffered() const
+{
+    auto& realm = this->realm();
+    auto& vm = realm.vm();
+
+    // FIXME: The buffered attribute must return a new static normalized TimeRanges object that represents the ranges of the
+    //        media resource, if any, that the user agent has buffered, at the time the attribute is evaluated. Users agents
+    //        must accurately determine the ranges available, even for media streams where this can only be determined by
+    //        tedious inspection.
+    return TRY(vm.heap().allocate<TimeRanges>(realm, realm));
+}
+
 // https://html.spec.whatwg.org/multipage/media.html#dom-navigator-canplaytype
 WebIDL::ExceptionOr<Bindings::CanPlayTypeResult> HTMLMediaElement::can_play_type(DeprecatedString const& type) const
 {