Experiment with redirecting all BrowserThreads (but UI/IO) to TaskScheduler

content/browser/browser_main_loop.h

 // 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.
 
 #ifndef CONTENT_BROWSER_BROWSER_MAIN_LOOP_H_
 #define CONTENT_BROWSER_BROWSER_MAIN_LOOP_H_
 
 #include <memory>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
 #include "content/browser/browser_process_sub_thread.h"
 #include "content/public/browser/browser_main_runner.h"
 #include "media/audio/audio_manager.h"
 
 #if defined(USE_AURA)
 namespace aura {
 class Env;
 }
 #endif
 
 namespace base {
 class CommandLine;
 class FilePath;
 class HighResolutionTimerManager;
+class MemoryPressureMonitor;
 class MessageLoop;
 class PowerMonitor;
+class SingleThreadTaskRunner;
 class SystemMonitor;
-class MemoryPressureMonitor;
 namespace trace_event {
 class TraceEventSystemStatsMonitor;
 }  // namespace trace_event
 }  // namespace base
 
 namespace device {
 class TimeZoneMonitor;
 }
 
 namespace media {
@@ skipping 222 matching lines @@
 
   // Members initialized in |PreCreateThreads()| -------------------------------
   // Torn down in ShutdownThreadsAndCleanUp.
   std::unique_ptr<base::MemoryPressureMonitor> memory_pressure_monitor_;
 #if defined(USE_X11) && !(OS_CHROMEOS)
   std::unique_ptr<internal::GpuDataManagerVisualProxy>
       gpu_data_manager_visual_proxy_;
 #endif
 
   // Members initialized in |CreateThreads()| ----------------------------------
   std::unique_ptr<BrowserProcessSubThread> db_thread_;

[Avi (use Gerrit), 2016/11/08 16:16:15]

Can you add commentary to this block as to when the "thread_" or "task_runner_"
variants are active?

[gab, 2016/11/08 20:40:44]

Done.

   std::unique_ptr<BrowserProcessSubThread> file_user_blocking_thread_;
   std::unique_ptr<BrowserProcessSubThread> file_thread_;
   std::unique_ptr<BrowserProcessSubThread> process_launcher_thread_;
   std::unique_ptr<BrowserProcessSubThread> cache_thread_;
+  scoped_refptr<base::SingleThreadTaskRunner> db_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> file_user_blocking_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> process_launcher_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> cache_task_runner_;
+  // The IO thread is never redirected to TaskScheduler at this point.
   std::unique_ptr<BrowserProcessSubThread> io_thread_;
 
   // Members initialized in |BrowserThreadsStarted()| --------------------------
   std::unique_ptr<base::Thread> indexed_db_thread_;
   std::unique_ptr<ServiceManagerContext> service_manager_context_;
   std::unique_ptr<mojo::edk::ScopedIPCSupport> mojo_ipc_support_;
 
   // |user_input_monitor_| has to outlive |audio_manager_|, so declared first.
   std::unique_ptr<media::UserInputMonitor> user_input_monitor_;
   // AudioThread needs to outlive |audio_manager_|.
@@ skipping 21 matching lines @@
   scoped_refptr<SaveFileManager> save_file_manager_;
 
   // DO NOT add members here. Add them to the right categories above.
 
   DISALLOW_COPY_AND_ASSIGN(BrowserMainLoop);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BROWSER_MAIN_LOOP_H_