LibWeb: Implement seeking for audio tracks

Userland/Libraries/LibWeb/HTML/AudioTrack.cpp

@@ -89,6 +89,17 @@ Duration AudioTrack::duration() const
     return Duration::from_milliseconds(static_cast<i64>(duration * 1000.0));
 }
 
+void AudioTrack::seek(double position, MediaSeekMode seek_mode)
+{
+    // FIXME: Implement seeking mode.
+    (void)seek_mode;
+
+    auto duration = static_cast<double>(this->duration().to_milliseconds()) / 1000.0;
+    position = position / duration * static_cast<double>(m_loader->total_samples());
+
+    m_loader->seek(position).release_value_but_fixme_should_propagate_errors();
+}
+
 void AudioTrack::visit_edges(Cell::Visitor& visitor)
 {
     Base::visit_edges(visitor);

Userland/Libraries/LibWeb/HTML/AudioTrack.h

@@ -26,6 +26,7 @@ public:
 
     Duration position() const;
     Duration duration() const;
+    void seek(double, MediaSeekMode);
 
     String const& id() const { return m_id; }
     String const& kind() const { return m_kind; }

Userland/Libraries/LibWeb/HTML/HTMLAudioElement.cpp

@@ -56,4 +56,11 @@ void HTMLAudioElement::on_paused()
     });
 }
 
+void HTMLAudioElement::on_seek(double position, MediaSeekMode seek_mode)
+{
+    audio_tracks()->for_each_enabled_track([&](auto& audio_track) {
+        audio_track.seek(position, seek_mode);
+    });
+}
+
 }

Userland/Libraries/LibWeb/HTML/HTMLAudioElement.h

@@ -28,6 +28,7 @@ private:
 
     virtual void on_playing() override;
     virtual void on_paused() override;
+    virtual void on_seek(double, MediaSeekMode) override;
 };
 
 }