Split "Online" and "Offline" AudioContext processing

Source/modules/webaudio/OfflineAudioContext.h

Index: Source/modules/webaudio/OfflineAudioContext.h
diff --git a/Source/modules/webaudio/OfflineAudioContext.h b/Source/modules/webaudio/OfflineAudioContext.h
index 99276e7cbb5e19dc7edf2934b67a726f2eed8d2a..5b9201d527ebb9907290959bbeb2cb4f093de5a2 100644
--- a/Source/modules/webaudio/OfflineAudioContext.h
+++ b/Source/modules/webaudio/OfflineAudioContext.h
@@ -40,6 +40,13 @@ public:
     virtual ~OfflineAudioContext();
 
     ScriptPromise startOfflineRendering(ScriptState*);
+
+    virtual ScriptPromise closeContext(ScriptState*) override final;
+    virtual ScriptPromise suspendContext(ScriptState*) override final;
+    virtual ScriptPromise resumeContext(ScriptState*) override final;
+
+    virtual bool hasRealtimeConstraint() override final { return false; }
+
 private:
     OfflineAudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
 };