Redirect BrowserThread::FILE at USER_VISIBLE instead of BACKGROUND priority.

content/browser/browser_main_loop.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/browser/browser_main_loop.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 1036 matching lines @@
         // On Windows, the FILE thread needs to have a UI message loop which
         // pumps messages in such a way that Google Update can communicate back
         // to us.
         // TODO(robliao): Need to support COM in TaskScheduler before
         // redirecting the FILE thread on Windows. http://crbug.com/662122
         thread_to_start = &file_thread_;
         options = ui_message_loop_options;
 #else
         if (redirect_nonUInonIO_browser_threads) {
           non_ui_non_io_task_runner_traits
-              .WithPriority(base::TaskPriority::BACKGROUND)
+              .WithPriority(base::TaskPriority::USER_VISIBLE)
               .WithShutdownBehavior(base::TaskShutdownBehavior::BLOCK_SHUTDOWN);
         } else {
           thread_to_start = &file_thread_;
           options = io_message_loop_options;
           options.timer_slack = base::TIMER_SLACK_MAXIMUM;
         }
 #endif
         break;
       case BrowserThread::PROCESS_LAUNCHER:
         TRACE_EVENT_BEGIN1("startup",
@@ skipping 721 matching lines @@
   if (!audio_manager_) {
     audio_thread_ = base::MakeUnique<AudioManagerThread>();
     audio_manager_ = media::AudioManager::Create(
         audio_thread_->task_runner(), audio_thread_->worker_task_runner(),
         MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
 }
 
 }  // namespace content