Added a kEchoCancellation constraint to turn off the audio processing.

content/content_renderer.gypi

 # Copyright (c) 2012 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.
 
 {
   'dependencies': [
     'content_common_mojo_bindings',
     '../gin/gin.gyp:gin',
     '../jingle/jingle.gyp:jingle_glue',
     '../media/media.gyp:media',
@@ skipping 236 matching lines @@
     'renderer/media/crypto/ppapi_decryptor.cc',
     'renderer/media/crypto/ppapi_decryptor.h',
     'renderer/media/crypto/proxy_decryptor.cc',
     'renderer/media/crypto/proxy_decryptor.h',
     'renderer/media/media_stream_audio_level_calculator.cc',
     'renderer/media/media_stream_audio_level_calculator.h',
     'renderer/media/media_stream_audio_renderer.cc',
     'renderer/media/media_stream_audio_renderer.h',
     'renderer/media/media_stream_center.h',
     'renderer/media/media_stream_client.h',
+    'renderer/media/media_stream_constraints_util.cc',
+    'renderer/media/media_stream_constraints_util.h',
     'renderer/media/media_stream_dependency_factory.h',
     'renderer/media/media_stream_dispatcher.h',
     'renderer/media/media_stream_dispatcher_eventhandler.h',
     'renderer/media/media_stream_impl.h',
     'renderer/media/media_stream_track.cc',
     'renderer/media/media_stream_track.h',
     'renderer/media/midi_dispatcher.cc',
     'renderer/media/midi_dispatcher.h',
     'renderer/media/midi_message_filter.cc',
     'renderer/media/midi_message_filter.h',
@@ skipping 514 matching lines @@
     }],
   ],
   'target_conditions': [
     ['OS=="android"', {
       'sources/': [
         ['include', '^renderer/render_view_linux\\.cc$'],
       ],
     }],
   ],
 }