LibWeb: Flesh out AudioBufferSourceNode buffer setter steps

Author: https://github.com/tcl3
Commit: 72ca91ad1a
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3099

Libraries/LibWeb/WebAudio/AudioBufferSourceNode.h

@@ -60,6 +60,8 @@ private:
     GC::Ref<AudioParam> m_playback_rate;
     GC::Ref<AudioParam> m_detune;
     bool m_loop { false };
+    // https://webaudio.github.io/web-audio-api/#dom-audiobuffersourcenode-buffer-set-slot
+    bool m_buffer_set { false };
     double m_loop_start { 0.0 };
     double m_loop_end { 0.0 };
 };