WebAudio: Add stub for AudioDestinationNode.destination

This is called by https://athenacrisis.com/ and passed through to
AudioNode.connect, which expects an AudioNode.

Implement this function enough so that we return an AudioNode so that
AudioNode.connect does not throw a TypeError.

Userland/Libraries/LibWeb/WebAudio/BaseAudioContext.cpp

@@ -10,6 +10,7 @@
 #include <LibWeb/HTML/EventNames.h>
 #include <LibWeb/WebAudio/AudioBuffer.h>
 #include <LibWeb/WebAudio/AudioBufferSourceNode.h>
+#include <LibWeb/WebAudio/AudioDestinationNode.h>
 #include <LibWeb/WebAudio/BaseAudioContext.h>
 #include <LibWeb/WebAudio/BiquadFilterNode.h>
 #include <LibWeb/WebAudio/DynamicsCompressorNode.h>
@@ -32,6 +33,24 @@ void BaseAudioContext::initialize(JS::Realm& realm)
     WEB_SET_PROTOTYPE_FOR_INTERFACE(BaseAudioContext);
 }
 
+void BaseAudioContext::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_destination);
+}
+
+// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-destination
+JS::NonnullGCPtr<AudioDestinationNode> BaseAudioContext::destination()
+{
+    auto& realm = this->realm();
+
+    dbgln("FIXME: Properly implement BaseAudioContext::destination");
+
+    if (!m_destination)
+        m_destination = realm.heap().allocate<AudioDestinationNode>(realm, realm, *this);
+    return *m_destination;
+}
+
 void BaseAudioContext::set_onstatechange(WebIDL::CallbackType* event_handler)
 {
     set_event_handler_attribute(HTML::EventNames::statechange, event_handler);

Userland/Libraries/LibWeb/WebAudio/BaseAudioContext.h

@@ -55,17 +55,22 @@ public:
     WebIDL::ExceptionOr<JS::NonnullGCPtr<DynamicsCompressorNode>> create_dynamics_compressor();
     JS::NonnullGCPtr<GainNode> create_gain();
 
+    JS::NonnullGCPtr<AudioDestinationNode> destination();
+
 protected:
     explicit BaseAudioContext(JS::Realm&, float m_sample_rate = 0);
 
     virtual void initialize(JS::Realm&) override;
 
+    virtual void visit_edges(Cell::Visitor& visitor) override;
+
 private:
     float m_sample_rate { 0 };
     double m_current_time { 0 };
 
     Bindings::AudioContextState m_control_thread_state = Bindings::AudioContextState::Suspended;
     Bindings::AudioContextState m_rendering_thread_state = Bindings::AudioContextState::Suspended;
+    JS::GCPtr<AudioDestinationNode> m_destination;
 };
 
 }

Userland/Libraries/LibWeb/WebAudio/BaseAudioContext.idl

@@ -2,6 +2,7 @@
 #import <DOM/EventHandler.idl>
 #import <WebAudio/AudioBuffer.idl>
 #import <WebAudio/AudioBufferSourceNode.idl>
+#import <WebAudio/AudioDestinationNode.idl>
 #import <WebAudio/DynamicsCompressorNode.idl>
 #import <WebAudio/GainNode.idl>
 #import <WebAudio/OscillatorNode.idl>
@@ -16,7 +17,7 @@ enum AudioContextState { "suspended", "running", "closed" };
 // https://webaudio.github.io/web-audio-api/#BaseAudioContext
 [Exposed=Window]
 interface BaseAudioContext : EventTarget {
-    [FIXME] readonly attribute AudioDestinationNode destination;
+    readonly attribute AudioDestinationNode destination;
     readonly attribute float sampleRate;
     readonly attribute double currentTime;
     [FIXME] readonly attribute AudioListener listener;