Disable renderToAssociatedSink by default.

content/renderer/media/user_media_client_impl.cc

 // 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.
 
 #include "content/renderer/media/user_media_client_impl.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 201 matching lines @@
   // if it isNull.
   if (user_media_request.isNull()) {
     // We are in a test.
     controls.audio.requested = true;
     controls.video.requested = true;
   } else {
     if (user_media_request.audio()) {
       controls.audio.requested = true;
       // Check if this input device should be used to select a matching output
       // device for audio rendering.
-      enable_automatic_output_device_selection = true;  // On by default.
       GetConstraintValueAsBoolean(
           user_media_request.audioConstraints(),
           &blink::WebMediaTrackConstraintSet::renderToAssociatedSink,
           &enable_automatic_output_device_selection);
     }
     if (user_media_request.video()) {
       controls.video.requested = true;
     }
     CopyBlinkRequestToStreamControls(user_media_request, &controls);
     security_origin = user_media_request.getSecurityOrigin();
@@ skipping 938 matching lines @@
       return;
     }
   }
 }
 
 bool UserMediaClientImpl::UserMediaRequestInfo::HasPendingSources() const {
   return !sources_waiting_for_callback_.empty();
 }
 
 }  // namespace content