Oilpan: WebAudio: Prepare to move AudioProcessor hierarchy to Oilpan heap.

Source/platform/audio/AudioProcessor.h

Index: Source/platform/audio/AudioProcessor.h
diff --git a/Source/platform/audio/AudioProcessor.h b/Source/platform/audio/AudioProcessor.h
index ec9e99460d61e62d80fb979e7ecf9debe1b3be63..aded735abfeddde1392db8bb80c45c182eb672b9 100644
--- a/Source/platform/audio/AudioProcessor.h
+++ b/Source/platform/audio/AudioProcessor.h
@@ -32,6 +32,7 @@
 #define AudioProcessor_h
 
 #include "platform/PlatformExport.h"
+#include "platform/heap/Handle.h"
 
 namespace blink {
 
@@ -41,7 +42,7 @@ class AudioBus;
 // where the number of input channels equals the number of output channels.  It can be used as one part of a complex DSP algorithm,
 // or as the processor for a basic (one input - one output) AudioNode.
 
-class PLATFORM_EXPORT AudioProcessor {
+class PLATFORM_EXPORT AudioProcessor : public NoBaseWillBeGarbageCollectedFinalized<AudioProcessor> {
 public:
     AudioProcessor(float sampleRate, unsigned numberOfChannels)
         : m_initialized(false)
@@ -51,6 +52,7 @@ public:
     }
 
     virtual ~AudioProcessor();
+    virtual void trace(Visitor*);
 
     // Full initialization can be done here instead of in the constructor.
     virtual void initialize() = 0;