Revert 179987

base/synchronization/waitable_event_watcher.h

Index: base/synchronization/waitable_event_watcher.h
===================================================================
--- base/synchronization/waitable_event_watcher.h	(revision 179992)
+++ base/synchronization/waitable_event_watcher.h	(working copy)
@@ -23,6 +23,7 @@
 class AsyncCallbackTask;
 class WaitableEvent;
 
+// -----------------------------------------------------------------------------
 // This class provides a way to wait on a WaitableEvent asynchronously.
 //
 // Each instance of this object can be waiting on a single WaitableEvent. When
@@ -31,13 +32,12 @@
 //
 // Typical usage:
 //
-//   class MyClass {
+//   class MyClass : public base::WaitableEventWatcher::Delegate {
 //    public:
 //     void DoStuffWhenSignaled(WaitableEvent *waitable_event) {
-//       watcher_.StartWatching(waitable_event,
-//           base::Bind(&MyClass::OnWaitableEventSignaled, this);
+//       watcher_.StartWatching(waitable_event, this);
 //     }
-//     void OnWaitableEventSignaled(WaitableEvent* waitable_event) {
+//     virtual void OnWaitableEventSignaled(WaitableEvent* waitable_event) {
 //       // OK, time to do stuff!
 //     }
 //    private:
@@ -57,56 +57,106 @@
 //
 // NOTE: you /are/ allowed to delete the WaitableEvent while still waiting on
 // it with a Watcher. It will act as if the event was never signaled.
+// -----------------------------------------------------------------------------
 
 class BASE_EXPORT WaitableEventWatcher
-#if defined(OS_WIN)
-    : public win::ObjectWatcher::Delegate {
-#else
-    : public MessageLoop::DestructionObserver {
+#if !defined(OS_WIN)
+    : public MessageLoop::DestructionObserver
 #endif
+{
  public:
-  typedef Callback<void(WaitableEvent*)> EventCallback;
+
   WaitableEventWatcher();
   virtual ~WaitableEventWatcher();
 
-  // When @event is signaled, the given callback is called on the thread of the
-  // current message loop when StartWatching is called.
-  bool StartWatching(WaitableEvent* event, const EventCallback& callback);
+  class BASE_EXPORT Delegate {
+   public:
+    // -------------------------------------------------------------------------
+    // This is called on the MessageLoop thread when WaitableEvent has been
+    // signaled.
+    //
+    // Note: the event may not be signaled by the time that this function is
+    // called. This indicates only that it has been signaled at some point in
+    // the past.
+    // -------------------------------------------------------------------------
+    virtual void OnWaitableEventSignaled(WaitableEvent* waitable_event) = 0;
 
+   protected:
+    virtual ~Delegate() { }
+  };
+
+  // ---------------------------------------------------------------------------
+  // When @event is signaled, the given delegate is called on the thread of the
+  // current message loop when StartWatching is called. The delegate is not
+  // deleted.
+  // ---------------------------------------------------------------------------
+  bool StartWatching(WaitableEvent* event, Delegate* delegate);
+
+  // ---------------------------------------------------------------------------
   // Cancel the current watch. Must be called from the same thread which
   // started the watch.
   //
   // Does nothing if no event is being watched, nor if the watch has completed.
-  // The callback will *not* be called for the current watch after this
-  // function returns. Since the callback runs on the same thread as this
+  // The delegate will *not* be called for the current watch after this
+  // function returns. Since the delegate runs on the same thread as this
   // function, it cannot be called during this function either.
+  // ---------------------------------------------------------------------------
   void StopWatching();
 
+  // ---------------------------------------------------------------------------
   // Return the currently watched event, or NULL if no object is currently being
   // watched.
+  // ---------------------------------------------------------------------------
   WaitableEvent* GetWatchedEvent();
 
-  // Return the callback that will be invoked when the event is
-  // signaled.
-  const EventCallback& callback() const { return callback_; }
+  // ---------------------------------------------------------------------------
+  // Return the delegate, or NULL if there is no delegate.
+  // ---------------------------------------------------------------------------
+  Delegate* delegate() {
+    return delegate_;
+  }
 
  private:
 #if defined(OS_WIN)
-  virtual void OnObjectSignaled(HANDLE h) OVERRIDE;
+  // ---------------------------------------------------------------------------
+  // The helper class exists because, if WaitableEventWatcher were to inherit
+  // from ObjectWatcher::Delegate, then it couldn't also have an inner class
+  // called Delegate (at least on Windows). Thus this object exists to proxy
+  // the callback function
+  // ---------------------------------------------------------------------------
+  class ObjectWatcherHelper : public win::ObjectWatcher::Delegate {
+   public:
+    ObjectWatcherHelper(WaitableEventWatcher* watcher);
+
+    // -------------------------------------------------------------------------
+    // Implementation of ObjectWatcher::Delegate
+    // -------------------------------------------------------------------------
+    void OnObjectSignaled(HANDLE h);
+
+   private:
+    WaitableEventWatcher *const watcher_;
+  };
+
+  void OnObjectSignaled();
+
+  ObjectWatcherHelper helper_;
   win::ObjectWatcher watcher_;
 #else
+  // ---------------------------------------------------------------------------
   // Implementation of MessageLoop::DestructionObserver
+  // ---------------------------------------------------------------------------
   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 
   MessageLoop* message_loop_;
   scoped_refptr<Flag> cancel_flag_;
   AsyncWaiter* waiter_;
-  base::Closure internal_callback_;
+  base::Closure callback_;
   scoped_refptr<WaitableEvent::WaitableEventKernel> kernel_;
 #endif
 
   WaitableEvent* event_;
-  EventCallback callback_;
+
+  Delegate* delegate_;
 };
 
 }  // namespace base