Implement IIRFilter node for WebAudio.

third_party/WebKit/Source/modules/webaudio/AudioNode.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 394 matching lines @@
     // AudioNodeInput::disable() where we want to disable outputs when there's only one connection
     // left because we're ready to go away, but can't quite yet.
     if (m_connectionRefCount <= 1 && !m_isDisabled) {
         // Still may have JavaScript references, but no more "active" connection references, so put all of our outputs in a "dormant" disabled state.
         // Garbage collection may take a very long time after this time, so the "dormant" disabled nodes should not bog down the rendering...
 
         // As far as JavaScript is concerned, our outputs must still appear to be connected.
         // But internally our outputs should be disabled from the inputs they're connected to.
         // disable() can recursively deref connections (and call disable()) down a whole chain of connected nodes.
 
-        // TODO(rtoy,hongchan): we special case the convolver, delay, and biquad since they have a
-        // significant tail-time and shouldn't be disconnected simply because they no longer have
-        // any input connections. This needs to be handled more generally where AudioNodes have a
-        // tailTime attribute. Then the AudioNode only needs to remain "active" for tailTime seconds
-        // after there are no longer any active connections.
+        // TODO(rtoy,hongchan): we need special cases the convolver, delay, biquad, and IIR since
+        // they have a significant tail-time and shouldn't be disconnected simply because they no
+        // longer have any input connections. This needs to be handled more generally where
+        // AudioNodes have a tailTime attribute. Then the AudioNode only needs to remain "active"
+        // for tailTime seconds after there are no longer any active connections.
         if (nodeType() != NodeTypeConvolver
             && nodeType() != NodeTypeDelay
-            && nodeType() != NodeTypeBiquadFilter) {
+            && nodeType() != NodeTypeBiquadFilter
+            && nodeType() != NodeTypeIIRFilter) {
             m_isDisabled = true;
             clearInternalStateWhenDisabled();
             for (auto& output : m_outputs)
                 output->disable();
         }
     }
 }
 
 void AudioHandler::makeConnection()
 {
@@ skipping 500 matching lines @@
 void AudioNode::didAddOutput(unsigned numberOfOutputs)
 {
     m_connectedNodes.append(nullptr);
     ASSERT_UNUSED(numberOfOutputs, numberOfOutputs == m_connectedNodes.size());
     m_connectedParams.append(nullptr);
     ASSERT_UNUSED(numberOfOutputs, numberOfOutputs == m_connectedParams.size());
 }
 
 } // namespace blink