Enable MessageLoop unittests on iOS and fix MessagePumpIOForIOS bug.

base/message_pump_io_ios.h

 // Copyright 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_IO_IOS_H_
 #define BASE_MESSAGE_PUMP_IO_IOS_H_
 
 #include "base/base_export.h"
 #include "base/mac/scoped_cffiledescriptorref.h"
 #include "base/mac/scoped_cftyperef.h"
+#include "base/memory/ref_counted.h"
 #include "base/message_pump_mac.h"
 #include "base/observer_list.h"
 
 namespace base {
 
 // This file introduces a class to monitor sockets and issue callbacks when
 // sockets are ready for I/O on iOS.
 class BASE_EXPORT MessagePumpIOSForIO : public MessagePumpNSRunLoop {
  public:
   class IOObserver {
@@ skipping 53 matching lines @@
 
     void set_watcher(Watcher* watcher) { watcher_ = watcher; }
 
     void OnFileCanReadWithoutBlocking(int fd, MessagePumpIOSForIO* pump);
     void OnFileCanWriteWithoutBlocking(int fd, MessagePumpIOSForIO* pump);
 
     bool is_persistent_;  // false if this event is one-shot.
     base::mac::ScopedCFFileDescriptorRef fdref_;
     CFOptionFlags callback_types_;
     base::mac::ScopedCFTypeRef<CFRunLoopSourceRef> fd_source_;
-    MessagePumpIOSForIO* pump_;
+    scoped_refptr<MessagePumpIOSForIO> pump_;

[wtc, 2012/12/03 19:27:18]

Do you know why the FileDescriptorWatcher class in
message_pump_libevent.h doesn't need to do this?
What is the solution used over there? Can we copy
that solution here?

I studied the code and may have found the answers to
my own questions.

It seems that an important difference between the libevent and
iOS versions of the
FileDescriptorWatcher::StopWatchingFileDescriptor function
is that the libevent version does not use |pump_|, so
|pump_| can be an invalid pointer, whereas the iOS version
needs a valid |pump_| for the
pump_->RemoveRunLoopSource(fd_source_) call to succeed.

Another solution would be to make the FileDescriptorWatcher
objects "observe" the |pump_| object, so that the |pump_|
object can notify the FileDescriptorWatcher objects that it
is going away. Alternatively, make |pump_| a weak pointer.
These alternative solutions would allow |pump_| to be
destroyed sooner. I don't know which solution is better though.

     Watcher* watcher_;
 
     DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher);
   };
 
   enum Mode {
     WATCH_READ = 1 << 0,
     WATCH_WRITE = 1 << 1,
     WATCH_READ_WRITE = WATCH_READ | WATCH_WRITE
   };
@@ skipping 37 matching lines @@
 
   ObserverList<IOObserver> io_observers_;
   ThreadChecker watch_file_descriptor_caller_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePumpIOSForIO);
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_PUMP_IO_IOS_H_