Made the AudioProcessing class a pure interface.

webrtc/modules/audio_processing/audio_processing_impl.cc

Index: webrtc/modules/audio_processing/audio_processing_impl.cc
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.cc b/webrtc/modules/audio_processing/audio_processing_impl.cc
index 85f159716cf9d49753fad1fdd18108971b922a9b..c892b7886c71a4ad78603484808cc4e82774e20e 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.cc
+++ b/webrtc/modules/audio_processing/audio_processing_impl.cc
@@ -1251,6 +1251,10 @@ int AudioProcessingImpl::StartDebugRecording(FILE* handle,
 #endif  // WEBRTC_AUDIOPROC_DEBUG_DUMP
 }
 
+int AudioProcessingImpl::StartDebugRecording(FILE* handle) {
+  return StartDebugRecording(handle, -1);
+}
+
 int AudioProcessingImpl::StartDebugRecordingForPlatformFile(
     rtc::PlatformFile handle) {
   // Run in a single-threaded manner.