Make AudioDebugFileWriter create its own file worker thread.

content/browser/speech/speech_recognizer_impl.cc

 // Copyright (c) 2013 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/browser/speech/speech_recognizer_impl.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
@@ skipping 619 matching lines @@
              << input_parameters.AsHumanReadableString();
   }
 
   // Create an audio converter which converts data between native input format
   // and WebSpeech specific output format.
   audio_converter_.reset(
       new OnDataConverter(input_parameters, output_parameters));
 
   audio_controller_ = AudioInputController::Create(
       GetAudioManager(), this, this, nullptr, input_parameters, device_id_,
-      /*agc_is_enabled*/ false,
-      BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE));
+      /*agc_is_enabled*/ false);
 
   if (!audio_controller_.get()) {
     return Abort(
         SpeechRecognitionError(SPEECH_RECOGNITION_ERROR_AUDIO_CAPTURE));
   }
 
   audio_log_->OnCreated(0, input_parameters, device_id_);
 
   // The endpointer needs to estimate the environment/background noise before
   // starting to treat the audio as user input. We wait in the state
@@ skipping 254 matching lines @@
       engine_error(SPEECH_RECOGNITION_ERROR_NONE) {
 }
 
 SpeechRecognizerImpl::FSMEventArgs::FSMEventArgs(const FSMEventArgs& other) =
     default;
 
 SpeechRecognizerImpl::FSMEventArgs::~FSMEventArgs() {
 }
 
 }  // namespace content