Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AudioDestinationNode.cpp

Index: Source/modules/webaudio/AudioDestinationNode.cpp
diff --git a/Source/modules/webaudio/AudioDestinationNode.cpp b/Source/modules/webaudio/AudioDestinationNode.cpp
index 920bb6cef15abd48fa14f9edccea93b494906984..3e64d1e79997a8a47515579eb0349fe5347ccc47 100644
--- a/Source/modules/webaudio/AudioDestinationNode.cpp
+++ b/Source/modules/webaudio/AudioDestinationNode.cpp
@@ -95,6 +95,12 @@ void AudioDestinationHandler::render(AudioBus* sourceBus, AudioBus* destinationB
     releaseStore(&m_currentSampleFrame, newSampleFrame);
 }
 
+WebThread* AudioDestinationHandler::offlineRenderThread()
+{
+    ASSERT_NOT_REACHED();
+    return nullptr;
+}
+
 // ----------------------------------------------------------------
 
 AudioDestinationNode::AudioDestinationNode(AudioContext& context)