Add a Mojo EDK for Chrome that uses one OS pipe per message pipe.

base/win/object_watcher.h

 // 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.
 
 #ifndef BASE_WIN_OBJECT_WATCHER_H_
 #define BASE_WIN_OBJECT_WATCHER_H_
 
 #include <windows.h>
 
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 
 namespace base {
 namespace win {
 
 // A class that provides a means to asynchronously wait for a Windows object to
 // become signaled.  It is an abstraction around RegisterWaitForSingleObject
 // that provides a notification callback, OnObjectSignaled, that runs back on
 // the origin thread (i.e., the thread that called StartWatching).
 //
 // This class acts like a smart pointer such that when it goes out-of-scope,
 // UnregisterWaitEx is automatically called, and any in-flight notification is
 // suppressed.
 //
 // Typical usage:
 //
-//   class MyClass : public base::ObjectWatcher::Delegate {
+//   class MyClass : public base::win::ObjectWatcher::Delegate {
 //    public:
 //     void DoStuffWhenSignaled(HANDLE object) {
 //       watcher_.StartWatching(object, this);
 //     }
-//     virtual void OnObjectSignaled(HANDLE object) {
+//     void OnObjectSignaled(HANDLE object) override {
 //       // OK, time to do stuff!
 //     }
 //    private:
-//     base::ObjectWatcher watcher_;
+//     base::win::ObjectWatcher watcher_;
 //   };
 //
 // In the above example, MyClass wants to "do stuff" when object becomes
 // signaled.  ObjectWatcher makes this task easy.  When MyClass goes out of
 // scope, the watcher_ will be destroyed, and there is no need to worry about
 // OnObjectSignaled being called on a deleted MyClass pointer.  Easy!
 // If the object is already signaled before being watched, OnObjectSignaled is
 // still called after (but not necessarily immediately after) watch is started.
 //
 class BASE_EXPORT ObjectWatcher : public MessageLoop::DestructionObserver {
  public:
   class BASE_EXPORT Delegate {
    public:
     virtual ~Delegate() {}
     // Called from the MessageLoop when a signaled object is detected.  To
     // continue watching the object, StartWatching must be called again.
     virtual void OnObjectSignaled(HANDLE object) = 0;
   };
 
   ObjectWatcher();
   ~ObjectWatcher() override;
 
   // When the object is signaled, the given delegate is notified on the thread
   // where StartWatching is called.  The ObjectWatcher is not responsible for
   // deleting the delegate.
+  // If |wait_many| is true, then this calls the callback each time it's

[yzshen1, 2015/09/23 22:47:08]

I feel that "execute_only_once" may be more clear, because "wait many" sounds
like we are waiting on multiple handles.

+  // signalled.
   //
   // Returns true if the watch was started.  Otherwise, false is returned.
   //
-  bool StartWatching(HANDLE object, Delegate* delegate);
+  bool StartWatching(HANDLE object, Delegate* delegate, bool wait_many);
 
   // Stops watching.  Does nothing if the watch has already completed.  If the
   // watch is still active, then it is canceled, and the associated delegate is
   // not notified.
   //
   // Returns true if the watch was canceled.  Otherwise, false is returned.
   //
   bool StopWatching();
 
   // Returns true if currently watching an object.
   bool IsWatching() const;
 
   // Returns the handle of the object being watched.
   HANDLE GetWatchedObject() const;
 
  private:
   // Called on a background thread when done waiting.
   static void CALLBACK DoneWaiting(void* param, BOOLEAN timed_out);
 
   void Signal(Delegate* delegate);
 
   // MessageLoop::DestructionObserver implementation:
   void WillDestroyCurrentMessageLoop() override;
 
   // Internal state.
   Closure callback_;
   HANDLE object_;             // The object being watched
   HANDLE wait_object_;        // Returned by RegisterWaitForSingleObject
   MessageLoop* origin_loop_;  // Used to get back to the origin thread
-
+  bool wait_many_;
   WeakPtrFactory<ObjectWatcher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectWatcher);
 };
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_WIN_OBJECT_WATCHER_H_