Provide an iOS message pump for IO implementation.

base/message_pump_libevent.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_PUMP_LIBEVENT_H_
 #define BASE_MESSAGE_PUMP_LIBEVENT_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 77 matching lines @@
     event* event_;
     MessagePumpLibevent* pump_;
     Watcher* watcher_;
     base::WeakPtrFactory<FileDescriptorWatcher> weak_factory_;
 
     DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher);
   };
 
   enum Mode {
     WATCH_READ = 1 << 0,
-    WATCH_WRITE = 1 << 1,
-    WATCH_READ_WRITE = WATCH_READ | WATCH_WRITE
+    WATCH_WRITE = 1 << 1
   };
 
   MessagePumpLibevent();
 
   // Have the current thread's message loop watch for a a situation in which
   // reading/writing to the FD can be performed without blocking.
   // Callers must provide a preallocated FileDescriptorWatcher object which
   // can later be used to manage the lifetime of this event.
   // If a FileDescriptorWatcher is passed in which is already attached to
   // an event, then the effect is cumulative i.e. after the call |controller|
   // will watch both the previous event and the new one.
   // If an error occurs while calling this method in a cumulative fashion, the
   // event previously attached to |controller| is aborted.
   // Returns true on success.
   // Must be called on the same thread the message_pump is running on.
   // TODO(dkegel): switch to edge-triggered readiness notification
   bool WatchFileDescriptor(int fd,
                            bool persistent,
-                           Mode mode,
+                           int mode,
                            FileDescriptorWatcher *controller,
                            Watcher *delegate);
 
   void AddIOObserver(IOObserver* obs);
   void RemoveIOObserver(IOObserver* obs);
 
   // MessagePump methods:
   virtual void Run(Delegate* delegate) OVERRIDE;
   virtual void Quit() OVERRIDE;
   virtual void ScheduleWork() OVERRIDE;
@@ skipping 43 matching lines @@
   event* wakeup_event_;
 
   ObserverList<IOObserver> io_observers_;
   ThreadChecker watch_file_descriptor_caller_checker_;
   DISALLOW_COPY_AND_ASSIGN(MessagePumpLibevent);
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_PUMP_LIBEVENT_H_