Move message_loop to the message_loop directory.

base/message_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 BASE_MESSAGE_LOOP_H_
-#define BASE_MESSAGE_LOOP_H_
-
-#include <queue>
-#include <string>
-
-#include "base/base_export.h"
-#include "base/basictypes.h"
-#include "base/callback_forward.h"
-#include "base/location.h"
-#include "base/memory/ref_counted.h"
-#include "base/message_loop/message_loop_proxy.h"
-#include "base/message_pump.h"
-#include "base/observer_list.h"
-#include "base/pending_task.h"
-#include "base/sequenced_task_runner_helpers.h"
-#include "base/synchronization/lock.h"
-#include "base/tracking_info.h"
-#include "base/time.h"
-
-#if defined(OS_WIN)
-// We need this to declare base::MessagePumpWin::Dispatcher, which we should
-// really just eliminate.
-#include "base/message_pump_win.h"
-#elif defined(OS_IOS)
-#include "base/message_pump_io_ios.h"
-#elif defined(OS_POSIX)
-#include "base/message_pump_libevent.h"
-#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
-
-#if defined(USE_AURA) && defined(USE_X11) && !defined(OS_NACL)
-#include "base/message_pump_aurax11.h"
-#elif defined(USE_OZONE) && !defined(OS_NACL)
-#include "base/message_pump_ozone.h"
-#else
-#include "base/message_pump_gtk.h"
-#endif
-
-#endif
-#endif
-
-namespace base {
-class HistogramBase;
-class MessageLoopLockTest;
-class RunLoop;
-class ThreadTaskRunnerHandle;
-#if defined(OS_ANDROID)
-class MessagePumpForUI;
-#endif
-
-// A MessageLoop is used to process events for a particular thread.  There is
-// at most one MessageLoop instance per thread.
-//
-// Events include at a minimum Task instances submitted to PostTask and its
-// variants.  Depending on the type of message pump used by the MessageLoop
-// other events such as UI messages may be processed.  On Windows APC calls (as
-// time permits) and signals sent to a registered set of HANDLEs may also be
-// processed.
-//
-// NOTE: Unless otherwise specified, a MessageLoop's methods may only be called
-// on the thread where the MessageLoop's Run method executes.
-//
-// NOTE: MessageLoop has task reentrancy protection.  This means that if a
-// task is being processed, a second task cannot start until the first task is
-// finished.  Reentrancy can happen when processing a task, and an inner
-// message pump is created.  That inner pump then processes native messages
-// which could implicitly start an inner task.  Inner message pumps are created
-// with dialogs (DialogBox), common dialogs (GetOpenFileName), OLE functions
-// (DoDragDrop), printer functions (StartDoc) and *many* others.
-//
-// Sample workaround when inner task processing is needed:
-//   HRESULT hr;
-//   {
-//     MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
-//     hr = DoDragDrop(...); // Implicitly runs a modal message loop.
-//   }
-//   // Process |hr| (the result returned by DoDragDrop()).
-//
-// Please be SURE your task is reentrant (nestable) and all global variables
-// are stable and accessible before calling SetNestableTasksAllowed(true).
-//
-class BASE_EXPORT MessageLoop : public base::MessagePump::Delegate {
- public:
-
-#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
-  typedef base::MessagePumpDispatcher Dispatcher;
-  typedef base::MessagePumpObserver Observer;
-#endif
-
-  // A MessageLoop has a particular type, which indicates the set of
-  // asynchronous events it may process in addition to tasks and timers.
-  //
-  // TYPE_DEFAULT
-  //   This type of ML only supports tasks and timers.
-  //
-  // TYPE_UI
-  //   This type of ML also supports native UI events (e.g., Windows messages).
-  //   See also MessageLoopForUI.
-  //
-  // TYPE_IO
-  //   This type of ML also supports asynchronous IO.  See also
-  //   MessageLoopForIO.
-  //
-  enum Type {
-    TYPE_DEFAULT,
-    TYPE_UI,
-    TYPE_IO
-  };
-
-  // Normally, it is not necessary to instantiate a MessageLoop.  Instead, it
-  // is typical to make use of the current thread's MessageLoop instance.
-  explicit MessageLoop(Type type = TYPE_DEFAULT);
-  virtual ~MessageLoop();
-
-  // Returns the MessageLoop object for the current thread, or null if none.
-  static MessageLoop* current();
-
-  static void EnableHistogrammer(bool enable_histogrammer);
-
-  typedef base::MessagePump* (MessagePumpFactory)();
-  // Uses the given base::MessagePumpForUIFactory to override the default
-  // MessagePump implementation for 'TYPE_UI'. Returns true if the factory
-  // was successfully registered.
-  static bool InitMessagePumpForUIFactory(MessagePumpFactory* factory);
-
-  // A DestructionObserver is notified when the current MessageLoop is being
-  // destroyed.  These observers are notified prior to MessageLoop::current()
-  // being changed to return NULL.  This gives interested parties the chance to
-  // do final cleanup that depends on the MessageLoop.
-  //
-  // NOTE: Any tasks posted to the MessageLoop during this notification will
-  // not be run.  Instead, they will be deleted.
-  //
-  class BASE_EXPORT DestructionObserver {
-   public:
-    virtual void WillDestroyCurrentMessageLoop() = 0;
-
-   protected:
-    virtual ~DestructionObserver();
-  };
-
-  // Add a DestructionObserver, which will start receiving notifications
-  // immediately.
-  void AddDestructionObserver(DestructionObserver* destruction_observer);
-
-  // Remove a DestructionObserver.  It is safe to call this method while a
-  // DestructionObserver is receiving a notification callback.
-  void RemoveDestructionObserver(DestructionObserver* destruction_observer);
-
-  // The "PostTask" family of methods call the task's Run method asynchronously
-  // from within a message loop at some point in the future.
-  //
-  // With the PostTask variant, tasks are invoked in FIFO order, inter-mixed
-  // with normal UI or IO event processing.  With the PostDelayedTask variant,
-  // tasks are called after at least approximately 'delay_ms' have elapsed.
-  //
-  // The NonNestable variants work similarly except that they promise never to
-  // dispatch the task from a nested invocation of MessageLoop::Run.  Instead,
-  // such tasks get deferred until the top-most MessageLoop::Run is executing.
-  //
-  // The MessageLoop takes ownership of the Task, and deletes it after it has
-  // been Run().
-  //
-  // PostTask(from_here, task) is equivalent to
-  // PostDelayedTask(from_here, task, 0).
-  //
-  // The TryPostTask is meant for the cases where the calling thread cannot
-  // block. If posting the task will block, the call returns false, the task
-  // is not posted but the task is consumed anyways.
-  //
-  // NOTE: These methods may be called on any thread.  The Task will be invoked
-  // on the thread that executes MessageLoop::Run().
-  void PostTask(
-      const tracked_objects::Location& from_here,
-      const base::Closure& task);
-
-  bool TryPostTask(
-      const tracked_objects::Location& from_here,
-      const base::Closure& task);
-
-  void PostDelayedTask(
-      const tracked_objects::Location& from_here,
-      const base::Closure& task,
-      base::TimeDelta delay);
-
-  void PostNonNestableTask(
-      const tracked_objects::Location& from_here,
-      const base::Closure& task);
-
-  void PostNonNestableDelayedTask(
-      const tracked_objects::Location& from_here,
-      const base::Closure& task,
-      base::TimeDelta delay);
-
-  // A variant on PostTask that deletes the given object.  This is useful
-  // if the object needs to live until the next run of the MessageLoop (for
-  // example, deleting a RenderProcessHost from within an IPC callback is not
-  // good).
-  //
-  // NOTE: This method may be called on any thread.  The object will be deleted
-  // on the thread that executes MessageLoop::Run().  If this is not the same
-  // as the thread that calls PostDelayedTask(FROM_HERE, ), then T MUST inherit
-  // from RefCountedThreadSafe<T>!
-  template <class T>
-  void DeleteSoon(const tracked_objects::Location& from_here, const T* object) {
-    base::subtle::DeleteHelperInternal<T, void>::DeleteViaSequencedTaskRunner(
-        this, from_here, object);
-  }
-
-  // A variant on PostTask that releases the given reference counted object
-  // (by calling its Release method).  This is useful if the object needs to
-  // live until the next run of the MessageLoop, or if the object needs to be
-  // released on a particular thread.
-  //
-  // NOTE: This method may be called on any thread.  The object will be
-  // released (and thus possibly deleted) on the thread that executes
-  // MessageLoop::Run().  If this is not the same as the thread that calls
-  // PostDelayedTask(FROM_HERE, ), then T MUST inherit from
-  // RefCountedThreadSafe<T>!
-  template <class T>
-  void ReleaseSoon(const tracked_objects::Location& from_here,
-                   const T* object) {
-    base::subtle::ReleaseHelperInternal<T, void>::ReleaseViaSequencedTaskRunner(
-        this, from_here, object);
-  }
-
-  // Deprecated: use RunLoop instead.
-  // Run the message loop.
-  void Run();
-
-  // Deprecated: use RunLoop instead.
-  // Process all pending tasks, windows messages, etc., but don't wait/sleep.
-  // Return as soon as all items that can be run are taken care of.
-  void RunUntilIdle();
-
-  // TODO(jbates) remove this. crbug.com/131220. See QuitWhenIdle().
-  void Quit() { QuitWhenIdle(); }
-
-  // Deprecated: use RunLoop instead.
-  //
-  // Signals the Run method to return when it becomes idle. It will continue to
-  // process pending messages and future messages as long as they are enqueued.
-  // Warning: if the MessageLoop remains busy, it may never quit. Only use this
-  // Quit method when looping procedures (such as web pages) have been shut
-  // down.
-  //
-  // This method may only be called on the same thread that called Run, and Run
-  // must still be on the call stack.
-  //
-  // Use QuitClosure variants if you need to Quit another thread's MessageLoop,
-  // but note that doing so is fairly dangerous if the target thread makes
-  // nested calls to MessageLoop::Run.  The problem being that you won't know
-  // which nested run loop you are quitting, so be careful!
-  void QuitWhenIdle();
-
-  // Deprecated: use RunLoop instead.
-  //
-  // This method is a variant of Quit, that does not wait for pending messages
-  // to be processed before returning from Run.
-  void QuitNow();
-
-  // TODO(jbates) remove this. crbug.com/131220. See QuitWhenIdleClosure().
-  static base::Closure QuitClosure() { return QuitWhenIdleClosure(); }
-
-  // Deprecated: use RunLoop instead.
-  // Construct a Closure that will call QuitWhenIdle(). Useful to schedule an
-  // arbitrary MessageLoop to QuitWhenIdle.
-  static base::Closure QuitWhenIdleClosure();
-
-  // Returns true if this loop is |type|. This allows subclasses (especially
-  // those in tests) to specialize how they are identified.
-  virtual bool IsType(Type type) const;
-
-  // Returns the type passed to the constructor.
-  Type type() const { return type_; }
-
-  // Optional call to connect the thread name with this loop.
-  void set_thread_name(const std::string& thread_name) {
-    DCHECK(thread_name_.empty()) << "Should not rename this thread!";
-    thread_name_ = thread_name;
-  }
-  const std::string& thread_name() const { return thread_name_; }
-
-  // Gets the message loop proxy associated with this message loop.
-  scoped_refptr<base::MessageLoopProxy> message_loop_proxy() {
-    return message_loop_proxy_.get();
-  }
-
-  // Enables or disables the recursive task processing. This happens in the case
-  // of recursive message loops. Some unwanted message loop may occurs when
-  // using common controls or printer functions. By default, recursive task
-  // processing is disabled.
-  //
-  // Please utilize |ScopedNestableTaskAllower| instead of calling these methods
-  // directly.  In general nestable message loops are to be avoided.  They are
-  // dangerous and difficult to get right, so please use with extreme caution.
-  //
-  // The specific case where tasks get queued is:
-  // - The thread is running a message loop.
-  // - It receives a task #1 and execute it.
-  // - The task #1 implicitly start a message loop, like a MessageBox in the
-  //   unit test. This can also be StartDoc or GetSaveFileName.
-  // - The thread receives a task #2 before or while in this second message
-  //   loop.
-  // - With NestableTasksAllowed set to true, the task #2 will run right away.
-  //   Otherwise, it will get executed right after task #1 completes at "thread
-  //   message loop level".
-  void SetNestableTasksAllowed(bool allowed);
-  bool NestableTasksAllowed() const;
-
-  // Enables nestable tasks on |loop| while in scope.
-  class ScopedNestableTaskAllower {
-   public:
-    explicit ScopedNestableTaskAllower(MessageLoop* loop)
-        : loop_(loop),
-          old_state_(loop_->NestableTasksAllowed()) {
-      loop_->SetNestableTasksAllowed(true);
-    }
-    ~ScopedNestableTaskAllower() {
-      loop_->SetNestableTasksAllowed(old_state_);
-    }
-
-   private:
-    MessageLoop* loop_;
-    bool old_state_;
-  };
-
-  // Enables or disables the restoration during an exception of the unhandled
-  // exception filter that was active when Run() was called. This can happen
-  // if some third party code call SetUnhandledExceptionFilter() and never
-  // restores the previous filter.
-  void set_exception_restoration(bool restore) {
-    exception_restoration_ = restore;
-  }
-
-  // Returns true if we are currently running a nested message loop.
-  bool IsNested();
-
-  // A TaskObserver is an object that receives task notifications from the
-  // MessageLoop.
-  //
-  // NOTE: A TaskObserver implementation should be extremely fast!
-  class BASE_EXPORT TaskObserver {
-   public:
-    TaskObserver();
-
-    // This method is called before processing a task.
-    virtual void WillProcessTask(const base::PendingTask& pending_task) = 0;
-
-    // This method is called after processing a task.
-    virtual void DidProcessTask(const base::PendingTask& pending_task) = 0;
-
-   protected:
-    virtual ~TaskObserver();
-  };
-
-  // These functions can only be called on the same thread that |this| is
-  // running on.
-  void AddTaskObserver(TaskObserver* task_observer);
-  void RemoveTaskObserver(TaskObserver* task_observer);
-
-  // Returns true if the message loop has high resolution timers enabled.
-  // Provided for testing.
-  bool high_resolution_timers_enabled() {
-#if defined(OS_WIN)
-    return !high_resolution_timer_expiration_.is_null();
-#else
-    return true;
-#endif
-  }
-
-  // When we go into high resolution timer mode, we will stay in hi-res mode
-  // for at least 1s.
-  static const int kHighResolutionTimerModeLeaseTimeMs = 1000;
-
-  // Asserts that the MessageLoop is "idle".
-  void AssertIdle() const;
-
-#if defined(OS_WIN)
-  void set_os_modal_loop(bool os_modal_loop) {
-    os_modal_loop_ = os_modal_loop;
-  }
-
-  bool os_modal_loop() const {
-    return os_modal_loop_;
-  }
-#endif  // OS_WIN
-
-  // Can only be called from the thread that owns the MessageLoop.
-  bool is_running() const;
-
-  //----------------------------------------------------------------------------
- protected:
-
-#if defined(OS_WIN)
-  base::MessagePumpWin* pump_win() {
-    return static_cast<base::MessagePumpWin*>(pump_.get());
-  }
-#elif defined(OS_POSIX) && !defined(OS_IOS)
-  base::MessagePumpLibevent* pump_libevent() {
-    return static_cast<base::MessagePumpLibevent*>(pump_.get());
-  }
-#endif
-
-  scoped_refptr<base::MessagePump> pump_;
-
- private:
-  friend class base::RunLoop;
-  friend class base::MessageLoopLockTest;
-
-  // A function to encapsulate all the exception handling capability in the
-  // stacks around the running of a main message loop.  It will run the message
-  // loop in a SEH try block or not depending on the set_SEH_restoration()
-  // flag invoking respectively RunInternalInSEHFrame() or RunInternal().
-  void RunHandler();
-
-#if defined(OS_WIN)
-  __declspec(noinline) void RunInternalInSEHFrame();
-#endif
-
-  // A surrounding stack frame around the running of the message loop that
-  // supports all saving and restoring of state, as is needed for any/all (ugly)
-  // recursive calls.
-  void RunInternal();
-
-  // Called to process any delayed non-nestable tasks.
-  bool ProcessNextDelayedNonNestableTask();
-
-  // Runs the specified PendingTask.
-  void RunTask(const base::PendingTask& pending_task);
-
-  // Calls RunTask or queues the pending_task on the deferred task list if it
-  // cannot be run right now.  Returns true if the task was run.
-  bool DeferOrRunPendingTask(const base::PendingTask& pending_task);
-
-  // Adds the pending task to delayed_work_queue_.
-  void AddToDelayedWorkQueue(const base::PendingTask& pending_task);
-
-  // This function attempts to add pending task to our incoming_queue_.
-  // The append can only possibly fail when |use_try_lock| is true.
-  //
-  // When |use_try_lock| is true, then this call will avoid blocking if
-  // the related lock is already held, and will in that case (when the
-  // lock is contended) fail to perform the append, and will return false.
-  //
-  // If the call succeeds to append to the queue, then this call
-  // will return true.
-  //
-  // In all cases, the caller retains ownership of |pending_task|, but this
-  // function will reset the value of pending_task->task.  This is needed to
-  // ensure that the posting call stack does not retain pending_task->task
-  // beyond this function call.
-  bool AddToIncomingQueue(base::PendingTask* pending_task, bool use_try_lock);
-
-  // Load tasks from the incoming_queue_ into work_queue_ if the latter is
-  // empty.  The former requires a lock to access, while the latter is directly
-  // accessible on this thread.
-  void ReloadWorkQueue();
-
-  // Delete tasks that haven't run yet without running them.  Used in the
-  // destructor to make sure all the task's destructors get called.  Returns
-  // true if some work was done.
-  bool DeletePendingTasks();
-
-  // Calculates the time at which a PendingTask should run.
-  base::TimeTicks CalculateDelayedRuntime(base::TimeDelta delay);
-
-  // Start recording histogram info about events and action IF it was enabled
-  // and IF the statistics recorder can accept a registration of our histogram.
-  void StartHistogrammer();
-
-  // Add occurrence of event to our histogram, so that we can see what is being
-  // done in a specific MessageLoop instance (i.e., specific thread).
-  // If message_histogram_ is NULL, this is a no-op.
-  void HistogramEvent(int event);
-
-  // base::MessagePump::Delegate methods:
-  virtual bool DoWork() OVERRIDE;
-  virtual bool DoDelayedWork(base::TimeTicks* next_delayed_work_time) OVERRIDE;
-  virtual bool DoIdleWork() OVERRIDE;
-
-  Type type_;
-
-  // A list of tasks that need to be processed by this instance.  Note that
-  // this queue is only accessed (push/pop) by our current thread.
-  base::TaskQueue work_queue_;
-
-  // Contains delayed tasks, sorted by their 'delayed_run_time' property.
-  base::DelayedTaskQueue delayed_work_queue_;
-
-  // A recent snapshot of Time::Now(), used to check delayed_work_queue_.
-  base::TimeTicks recent_time_;
-
-  // A queue of non-nestable tasks that we had to defer because when it came
-  // time to execute them we were in a nested message loop.  They will execute
-  // once we're out of nested message loops.
-  base::TaskQueue deferred_non_nestable_work_queue_;
-
-  ObserverList<DestructionObserver> destruction_observers_;
-
-  // A recursion block that prevents accidentally running additional tasks when
-  // insider a (accidentally induced?) nested message pump.
-  bool nestable_tasks_allowed_;
-
-  bool exception_restoration_;
-
-  std::string thread_name_;
-  // A profiling histogram showing the counts of various messages and events.
-  base::HistogramBase* message_histogram_;
-
-  // An incoming queue of tasks that are acquired under a mutex for processing
-  // on this instance's thread. These tasks have not yet been sorted out into
-  // items for our work_queue_ vs delayed_work_queue_.
-  base::TaskQueue incoming_queue_;
-  // Protect access to incoming_queue_.
-  mutable base::Lock incoming_queue_lock_;
-
-  base::RunLoop* run_loop_;
-
-#if defined(OS_WIN)
-  base::TimeTicks high_resolution_timer_expiration_;
-  // Should be set to true before calling Windows APIs like TrackPopupMenu, etc
-  // which enter a modal message loop.
-  bool os_modal_loop_;
-#endif
-
-  // The next sequence number to use for delayed tasks. Updating this counter is
-  // protected by incoming_queue_lock_.
-  int next_sequence_num_;
-
-  ObserverList<TaskObserver> task_observers_;
-
-  // The message loop proxy associated with this message loop, if one exists.
-  scoped_refptr<base::MessageLoopProxy> message_loop_proxy_;
-  scoped_ptr<base::ThreadTaskRunnerHandle> thread_task_runner_handle_;
-
-  template <class T, class R> friend class base::subtle::DeleteHelperInternal;
-  template <class T, class R> friend class base::subtle::ReleaseHelperInternal;
-
-  void DeleteSoonInternal(const tracked_objects::Location& from_here,
-                          void(*deleter)(const void*),
-                          const void* object);
-  void ReleaseSoonInternal(const tracked_objects::Location& from_here,
-                           void(*releaser)(const void*),
-                           const void* object);
-
-  DISALLOW_COPY_AND_ASSIGN(MessageLoop);
-};
-
-//-----------------------------------------------------------------------------
-// MessageLoopForUI extends MessageLoop with methods that are particular to a
-// MessageLoop instantiated with TYPE_UI.
-//
-// This class is typically used like so:
-//   MessageLoopForUI::current()->...call some method...
-//
-class BASE_EXPORT MessageLoopForUI : public MessageLoop {
- public:
-#if defined(OS_WIN)
-  typedef base::MessagePumpForUI::MessageFilter MessageFilter;
-#endif
-
-  MessageLoopForUI() : MessageLoop(TYPE_UI) {
-  }
-
-  // Returns the MessageLoopForUI of the current thread.
-  static MessageLoopForUI* current() {
-    MessageLoop* loop = MessageLoop::current();
-    DCHECK(loop);
-    DCHECK_EQ(MessageLoop::TYPE_UI, loop->type());
-    return static_cast<MessageLoopForUI*>(loop);
-  }
-
-#if defined(OS_WIN)
-  void DidProcessMessage(const MSG& message);
-#endif  // defined(OS_WIN)
-
-#if defined(OS_IOS)
-  // On iOS, the main message loop cannot be Run().  Instead call Attach(),
-  // which connects this MessageLoop to the UI thread's CFRunLoop and allows
-  // PostTask() to work.
-  void Attach();
-#endif
-
-#if defined(OS_ANDROID)
-  // On Android, the UI message loop is handled by Java side. So Run() should
-  // never be called. Instead use Start(), which will forward all the native UI
-  // events to the Java message loop.
-  void Start();
-#elif !defined(OS_MACOSX)
-
-  // Please see message_pump_win/message_pump_glib for definitions of these
-  // methods.
-  void AddObserver(Observer* observer);
-  void RemoveObserver(Observer* observer);
-
-#if defined(OS_WIN)
-  // Plese see MessagePumpForUI for definitions of this method.
-  void SetMessageFilter(scoped_ptr<MessageFilter> message_filter) {
-    pump_ui()->SetMessageFilter(message_filter.Pass());
-  }
-#endif
-
- protected:
-#if defined(USE_AURA) && defined(USE_X11) && !defined(OS_NACL)
-  friend class base::MessagePumpAuraX11;
-#endif
-#if defined(USE_OZONE) && !defined(OS_NACL)
-  friend class base::MessagePumpOzone;
-#endif
-
-  // TODO(rvargas): Make this platform independent.
-  base::MessagePumpForUI* pump_ui() {
-    return static_cast<base::MessagePumpForUI*>(pump_.get());
-  }
-#endif  // !defined(OS_MACOSX)
-};
-
-// Do not add any member variables to MessageLoopForUI!  This is important b/c
-// MessageLoopForUI is often allocated via MessageLoop(TYPE_UI).  Any extra
-// data that you need should be stored on the MessageLoop's pump_ instance.
-COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForUI),
-               MessageLoopForUI_should_not_have_extra_member_variables);
-
-//-----------------------------------------------------------------------------
-// MessageLoopForIO extends MessageLoop with methods that are particular to a
-// MessageLoop instantiated with TYPE_IO.
-//
-// This class is typically used like so:
-//   MessageLoopForIO::current()->...call some method...
-//
-class BASE_EXPORT MessageLoopForIO : public MessageLoop {
- public:
-#if defined(OS_WIN)
-  typedef base::MessagePumpForIO::IOHandler IOHandler;
-  typedef base::MessagePumpForIO::IOContext IOContext;
-  typedef base::MessagePumpForIO::IOObserver IOObserver;
-#elif defined(OS_IOS)
-  typedef base::MessagePumpIOSForIO::Watcher Watcher;
-  typedef base::MessagePumpIOSForIO::FileDescriptorWatcher
-      FileDescriptorWatcher;
-  typedef base::MessagePumpIOSForIO::IOObserver IOObserver;
-
-  enum Mode {
-    WATCH_READ = base::MessagePumpIOSForIO::WATCH_READ,
-    WATCH_WRITE = base::MessagePumpIOSForIO::WATCH_WRITE,
-    WATCH_READ_WRITE = base::MessagePumpIOSForIO::WATCH_READ_WRITE
-  };
-#elif defined(OS_POSIX)
-  typedef base::MessagePumpLibevent::Watcher Watcher;
-  typedef base::MessagePumpLibevent::FileDescriptorWatcher
-      FileDescriptorWatcher;
-  typedef base::MessagePumpLibevent::IOObserver IOObserver;
-
-  enum Mode {
-    WATCH_READ = base::MessagePumpLibevent::WATCH_READ,
-    WATCH_WRITE = base::MessagePumpLibevent::WATCH_WRITE,
-    WATCH_READ_WRITE = base::MessagePumpLibevent::WATCH_READ_WRITE
-  };
-
-#endif
-
-  MessageLoopForIO() : MessageLoop(TYPE_IO) {
-  }
-
-  // Returns the MessageLoopForIO of the current thread.
-  static MessageLoopForIO* current() {
-    MessageLoop* loop = MessageLoop::current();
-    DCHECK_EQ(MessageLoop::TYPE_IO, loop->type());
-    return static_cast<MessageLoopForIO*>(loop);
-  }
-
-  void AddIOObserver(IOObserver* io_observer) {
-    pump_io()->AddIOObserver(io_observer);
-  }
-
-  void RemoveIOObserver(IOObserver* io_observer) {
-    pump_io()->RemoveIOObserver(io_observer);
-  }
-
-#if defined(OS_WIN)
-  // Please see MessagePumpWin for definitions of these methods.
-  void RegisterIOHandler(HANDLE file, IOHandler* handler);
-  bool RegisterJobObject(HANDLE job, IOHandler* handler);
-  bool WaitForIOCompletion(DWORD timeout, IOHandler* filter);
-
- protected:
-  // TODO(rvargas): Make this platform independent.
-  base::MessagePumpForIO* pump_io() {
-    return static_cast<base::MessagePumpForIO*>(pump_.get());
-  }
-
-#elif defined(OS_IOS)
-  // Please see MessagePumpIOSForIO for definition.
-  bool WatchFileDescriptor(int fd,
-                           bool persistent,
-                           Mode mode,
-                           FileDescriptorWatcher *controller,
-                           Watcher *delegate);
-
- private:
-  base::MessagePumpIOSForIO* pump_io() {
-    return static_cast<base::MessagePumpIOSForIO*>(pump_.get());
-  }
-
-#elif defined(OS_POSIX)
-  // Please see MessagePumpLibevent for definition.
-  bool WatchFileDescriptor(int fd,
-                           bool persistent,
-                           Mode mode,
-                           FileDescriptorWatcher* controller,
-                           Watcher* delegate);
-
- private:
-  base::MessagePumpLibevent* pump_io() {
-    return static_cast<base::MessagePumpLibevent*>(pump_.get());
-  }
-#endif  // defined(OS_POSIX)
-};
-
-// Do not add any member variables to MessageLoopForIO!  This is important b/c
-// MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
-// data that you need should be stored on the MessageLoop's pump_ instance.
-COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
-               MessageLoopForIO_should_not_have_extra_member_variables);
-
-}  // namespace base
-
-#endif  // BASE_MESSAGE_LOOP_H_
+// TODO(brettw) remove this forwarding header when all callers have been
+// updatded.
+#include "base/message_loop/message_loop.h"