Salient parts of http://codereview.chromium.org/8392042/

content/browser/browser_thread.cc

Index: content/browser/browser_thread.cc
diff --git a/content/browser/browser_thread.cc b/content/browser/browser_thread.cc
deleted file mode 100644
index c3b400540e8d8897a68ea7cccccd4340f4b65908..0000000000000000000000000000000000000000
--- a/content/browser/browser_thread.cc
+++ /dev/null
@@ -1,340 +0,0 @@
-// Copyright (c) 2011 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_thread.h"
-
-#include "base/bind.h"
-#include "base/message_loop.h"
-#include "base/message_loop_proxy.h"
-#include "base/threading/thread_restrictions.h"
-
-// Friendly names for the well-known threads.
-static const char* browser_thread_names[BrowserThread::ID_COUNT] = {
-  "",  // UI (name assembled in browser_main.cc).
-  "Chrome_DBThread",  // DB
-  "Chrome_WebKitThread",  // WEBKIT
-  "Chrome_FileThread",  // FILE
-  "Chrome_ProcessLauncherThread",  // PROCESS_LAUNCHER
-  "Chrome_CacheThread",  // CACHE
-  "Chrome_IOThread",  // IO
-#if defined(OS_CHROMEOS)
-  "Chrome_WebSocketproxyThread",  // WEB_SOCKET_PROXY
-#endif
-};
-
-// An implementation of MessageLoopProxy to be used in conjunction
-// with BrowserThread.
-class BrowserThreadMessageLoopProxy : public base::MessageLoopProxy {
- public:
-  explicit BrowserThreadMessageLoopProxy(BrowserThread::ID identifier)
-      : id_(identifier) {
-  }
-
-  // MessageLoopProxy implementation.
-  virtual bool PostTask(const tracked_objects::Location& from_here,
-                        Task* task) {
-    return BrowserThread::PostTask(id_, from_here, task);
-  }
-
-  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
-                               Task* task, int64 delay_ms) {
-    return BrowserThread::PostDelayedTask(id_, from_here, task, delay_ms);
-  }
-
-  virtual bool PostNonNestableTask(const tracked_objects::Location& from_here,
-                                   Task* task) {
-    return BrowserThread::PostNonNestableTask(id_, from_here, task);
-  }
-
-  virtual bool PostNonNestableDelayedTask(
-      const tracked_objects::Location& from_here,
-      Task* task,
-      int64 delay_ms) {
-    return BrowserThread::PostNonNestableDelayedTask(id_, from_here, task,
-                                                    delay_ms);
-  }
-
-  virtual bool PostTask(const tracked_objects::Location& from_here,
-                        const base::Closure& task) {
-    return BrowserThread::PostTask(id_, from_here, task);
-  }
-
-  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
-                               const base::Closure& task, int64 delay_ms) {
-    return BrowserThread::PostDelayedTask(id_, from_here, task, delay_ms);
-  }
-
-  virtual bool PostNonNestableTask(const tracked_objects::Location& from_here,
-                                   const base::Closure& task) {
-    return BrowserThread::PostNonNestableTask(id_, from_here, task);
-  }
-
-  virtual bool PostNonNestableDelayedTask(
-      const tracked_objects::Location& from_here,
-      const base::Closure& task,
-      int64 delay_ms) {
-    return BrowserThread::PostNonNestableDelayedTask(id_, from_here, task,
-                                                     delay_ms);
-  }
-
-  virtual bool BelongsToCurrentThread() {
-    return BrowserThread::CurrentlyOn(id_);
-  }
-
- private:
-  BrowserThread::ID id_;
-  DISALLOW_COPY_AND_ASSIGN(BrowserThreadMessageLoopProxy);
-};
-
-
-base::Lock BrowserThread::lock_;
-
-BrowserThread* BrowserThread::browser_threads_[ID_COUNT];
-
-BrowserThread::BrowserThread(BrowserThread::ID identifier)
-    : Thread(browser_thread_names[identifier]),
-      identifier_(identifier) {
-  Initialize();
-}
-
-BrowserThread::BrowserThread(ID identifier, MessageLoop* message_loop)
-    : Thread(message_loop->thread_name().c_str()),
-      identifier_(identifier) {
-  set_message_loop(message_loop);
-  Initialize();
-}
-
-void BrowserThread::Initialize() {
-  base::AutoLock lock(lock_);
-  DCHECK(identifier_ >= 0 && identifier_ < ID_COUNT);
-  DCHECK(browser_threads_[identifier_] == NULL);
-  browser_threads_[identifier_] = this;
-}
-
-BrowserThread::~BrowserThread() {
-  // Stop the thread here, instead of the parent's class destructor.  This is so
-  // that if there are pending tasks that run, code that checks that it's on the
-  // correct BrowserThread succeeds.
-  Stop();
-
-  base::AutoLock lock(lock_);
-  browser_threads_[identifier_] = NULL;
-#ifndef NDEBUG
-  // Double check that the threads are ordered correctly in the enumeration.
-  for (int i = identifier_ + 1; i < ID_COUNT; ++i) {
-    DCHECK(!browser_threads_[i]) <<
-        "Threads must be listed in the reverse order that they die";
-  }
-#endif
-}
-
-// static
-bool BrowserThread::IsWellKnownThread(ID identifier) {
-  base::AutoLock lock(lock_);
-  return (identifier >= 0 && identifier < ID_COUNT &&
-          browser_threads_[identifier]);
-}
-
-// static
-bool BrowserThread::CurrentlyOn(ID identifier) {
-  // We shouldn't use MessageLoop::current() since it uses LazyInstance which
-  // may be deleted by ~AtExitManager when a WorkerPool thread calls this
-  // function.
-  // http://crbug.com/63678
-  base::ThreadRestrictions::ScopedAllowSingleton allow_singleton;
-  base::AutoLock lock(lock_);
-  DCHECK(identifier >= 0 && identifier < ID_COUNT);
-  return browser_threads_[identifier] &&
-         browser_threads_[identifier]->message_loop() == MessageLoop::current();
-}
-
-// static
-bool BrowserThread::IsMessageLoopValid(ID identifier) {
-  base::AutoLock lock(lock_);
-  DCHECK(identifier >= 0 && identifier < ID_COUNT);
-  return browser_threads_[identifier] &&
-         browser_threads_[identifier]->message_loop();
-}
-
-// static
-bool BrowserThread::PostTask(ID identifier,
-                            const tracked_objects::Location& from_here,
-                            const base::Closure& task) {
-  return PostTaskHelper(identifier, from_here, task, 0, true);
-}
-
-// static
-bool BrowserThread::PostDelayedTask(ID identifier,
-                                   const tracked_objects::Location& from_here,
-                                   const base::Closure& task,
-                                   int64 delay_ms) {
-  return PostTaskHelper(identifier, from_here, task, delay_ms, true);
-}
-
-// static
-bool BrowserThread::PostNonNestableTask(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    const base::Closure& task) {
-  return PostTaskHelper(identifier, from_here, task, 0, false);
-}
-
-// static
-bool BrowserThread::PostNonNestableDelayedTask(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    const base::Closure& task,
-    int64 delay_ms) {
-  return PostTaskHelper(identifier, from_here, task, delay_ms, false);
-}
-
-// static
-bool BrowserThread::PostTask(ID identifier,
-                            const tracked_objects::Location& from_here,
-                            Task* task) {
-  return PostTaskHelper(identifier, from_here, task, 0, true);
-}
-
-// static
-bool BrowserThread::PostDelayedTask(ID identifier,
-                                   const tracked_objects::Location& from_here,
-                                   Task* task,
-                                   int64 delay_ms) {
-  return PostTaskHelper(identifier, from_here, task, delay_ms, true);
-}
-
-// static
-bool BrowserThread::PostNonNestableTask(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    Task* task) {
-  return PostTaskHelper(identifier, from_here, task, 0, false);
-}
-
-// static
-bool BrowserThread::PostNonNestableDelayedTask(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    Task* task,
-    int64 delay_ms) {
-  return PostTaskHelper(identifier, from_here, task, delay_ms, false);
-}
-
-// static
-bool BrowserThread::PostTaskAndReply(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    const base::Closure& task,
-    const base::Closure& reply) {
-  return GetMessageLoopProxyForThread(identifier)->PostTaskAndReply(from_here,
-                                                                    task,
-                                                                    reply);
-}
-
-// static
-bool BrowserThread::GetCurrentThreadIdentifier(ID* identifier) {
-  // We shouldn't use MessageLoop::current() since it uses LazyInstance which
-  // may be deleted by ~AtExitManager when a WorkerPool thread calls this
-  // function.
-  // http://crbug.com/63678
-  base::ThreadRestrictions::ScopedAllowSingleton allow_singleton;
-  MessageLoop* cur_message_loop = MessageLoop::current();
-  for (int i = 0; i < ID_COUNT; ++i) {
-    if (browser_threads_[i] &&
-        browser_threads_[i]->message_loop() == cur_message_loop) {
-      *identifier = browser_threads_[i]->identifier_;
-      return true;
-    }
-  }
-
-  return false;
-}
-
-// static
-scoped_refptr<base::MessageLoopProxy>
-BrowserThread::GetMessageLoopProxyForThread(
-    ID identifier) {
-  scoped_refptr<base::MessageLoopProxy> proxy(
-      new BrowserThreadMessageLoopProxy(identifier));
-  return proxy;
-}
-
-// static
-bool BrowserThread::PostTaskHelper(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    Task* task,
-    int64 delay_ms,
-    bool nestable) {
-  DCHECK(identifier >= 0 && identifier < ID_COUNT);
-  // Optimization: to avoid unnecessary locks, we listed the ID enumeration in
-  // order of lifetime.  So no need to lock if we know that the other thread
-  // outlives this one.
-  // Note: since the array is so small, ok to loop instead of creating a map,
-  // which would require a lock because std::map isn't thread safe, defeating
-  // the whole purpose of this optimization.
-  ID current_thread;
-  bool guaranteed_to_outlive_target_thread =
-      GetCurrentThreadIdentifier(&current_thread) &&
-      current_thread >= identifier;
-
-  if (!guaranteed_to_outlive_target_thread)
-    lock_.Acquire();
-
-  MessageLoop* message_loop = browser_threads_[identifier] ?
-      browser_threads_[identifier]->message_loop() : NULL;
-  if (message_loop) {
-    if (nestable) {
-      message_loop->PostDelayedTask(from_here, task, delay_ms);
-    } else {
-      message_loop->PostNonNestableDelayedTask(from_here, task, delay_ms);
-    }
-  }
-
-  if (!guaranteed_to_outlive_target_thread)
-    lock_.Release();
-
-  if (!message_loop)
-    delete task;
-
-  return !!message_loop;
-}
-
-// static
-bool BrowserThread::PostTaskHelper(
-    ID identifier,
-    const tracked_objects::Location& from_here,
-    const base::Closure& task,
-    int64 delay_ms,
-    bool nestable) {
-  DCHECK(identifier >= 0 && identifier < ID_COUNT);
-  // Optimization: to avoid unnecessary locks, we listed the ID enumeration in
-  // order of lifetime.  So no need to lock if we know that the other thread
-  // outlives this one.
-  // Note: since the array is so small, ok to loop instead of creating a map,
-  // which would require a lock because std::map isn't thread safe, defeating
-  // the whole purpose of this optimization.
-  ID current_thread;
-  bool guaranteed_to_outlive_target_thread =
-      GetCurrentThreadIdentifier(&current_thread) &&
-      current_thread >= identifier;
-
-  if (!guaranteed_to_outlive_target_thread)
-    lock_.Acquire();
-
-  MessageLoop* message_loop = browser_threads_[identifier] ?
-      browser_threads_[identifier]->message_loop() : NULL;
-  if (message_loop) {
-    if (nestable) {
-      message_loop->PostDelayedTask(from_here, task, delay_ms);
-    } else {
-      message_loop->PostNonNestableDelayedTask(from_here, task, delay_ms);
-    }
-  }
-
-  if (!guaranteed_to_outlive_target_thread)
-    lock_.Release();
-
-  return !!message_loop;
-}