Adds MessageLoopUIApplication for use on iOS.

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>
 
@@ skipping 530 matching lines @@
     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);
@@ skipping 83 matching lines @@
 #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);
 
 #endif  // BASE_MESSAGE_LOOP_H_