Added a kEchoCancellation constraint to turn off the audio processing.

content/renderer/media/media_stream_source.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_MEDIA_STREAM_SOURCE_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_SOURCE_H_
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
 
 namespace blink {
 class WebMediaStreamTrack;
 }  // namespace blink
 
 namespace content {
 
 class CONTENT_EXPORT MediaStreamSource
     : NON_EXPORTED_BASE(public blink::WebMediaStreamSource::ExtraData) {
  public:
   typedef base::Callback<void(const blink::WebMediaStreamSource& source)>
       SourceStoppedCallback;
 
   typedef base::Callback<void(MediaStreamSource* source,
                               bool success)> ConstraintsCallback;
 
+  // Source constraints key for
+  // http://dev.w3.org/2011/webrtc/editor/getusermedia.html.
+  static const char kSourceId[];
+
   MediaStreamSource();
   virtual ~MediaStreamSource();
 
   // Returns device information about a source that has been created by a
   // JavaScript call to GetUserMedia, e.g., a camera or microphone.
   const StreamDeviceInfo& device_info() const {
     return device_info_;
   }
 
   // Stops the source (by calling DoStopSource()). This sets the
@@ skipping 26 matching lines @@
  private:
   StreamDeviceInfo device_info_;
   SourceStoppedCallback stop_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_SOURCE_H_