Added a kEchoCancellation constraint to turn off the audio processing.

content/renderer/media/media_stream_audio_processor.h

Index: content/renderer/media/media_stream_audio_processor.h
diff --git a/content/renderer/media/media_stream_audio_processor.h b/content/renderer/media/media_stream_audio_processor.h
index 0c8051418d8ff6f8d6567f6f29257f3bb7ff832f..84f2d841e76beddb052fd0a751903687c74caeb7 100644
--- a/content/renderer/media/media_stream_audio_processor.h
+++ b/content/renderer/media/media_stream_audio_processor.h
@@ -11,7 +11,6 @@
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
-#include "content/public/common/media_stream_request.h"
 #include "content/renderer/media/webrtc_audio_device_impl.h"
 #include "media/base/audio_converter.h"
 #include "third_party/libjingle/source/talk/app/webrtc/mediastreaminterface.h"
@@ -52,7 +51,6 @@ class CONTENT_EXPORT MediaStreamAudioProcessor :
   // |playout_data_source| won't be used.
   MediaStreamAudioProcessor(const blink::WebMediaConstraints& constraints,
                             int effects,
-                            MediaStreamType type,
                             WebRtcPlayoutDataSource* playout_data_source);
 
   // Called when format of the capture data has changed.
@@ -123,8 +121,7 @@ class CONTENT_EXPORT MediaStreamAudioProcessor :
 
   // Helper to initialize the WebRtc AudioProcessing.
   void InitializeAudioProcessingModule(
-      const blink::WebMediaConstraints& constraints, int effects,
-      MediaStreamType type);
+      const blink::WebMediaConstraints& constraints, int effects);
 
   // Helper to initialize the capture converter.
   void InitializeCaptureConverter(const media::AudioParameters& source_params);
@@ -183,7 +180,7 @@ class CONTENT_EXPORT MediaStreamAudioProcessor :
   base::ThreadChecker render_thread_checker_;
 
   // Flag to enable the stereo channels mirroring.
-  bool audio_mirroring_;
+  bool goog_audio_mirroring_;
 
   // Used by the typing detection.
   scoped_ptr<webrtc::TypingDetection> typing_detector_;
@@ -191,7 +188,7 @@ class CONTENT_EXPORT MediaStreamAudioProcessor :
   // This flag is used to show the result of typing detection.
   // It can be accessed by the capture audio thread and by the libjingle thread

[perkj_chrome, 2014/04/11 11:45:04]

is this still true? is libjingle thread involved?

[no longer working on chromium, 2014/04/11 16:47:05]

Yes, by GetStats() from libjingle.

   // which calls GetStats().
-  base::subtle::Atomic32 typing_detected_;
+  base::subtle::Atomic32 goog_typing_detected_;
 };
 
 }  // namespace content