Enable MessageLoop unittests on iOS and fix MessagePumpIOForIOS bug.

base/message_pump_io_ios.h

Index: base/message_pump_io_ios.h
diff --git a/base/message_pump_io_ios.h b/base/message_pump_io_ios.h
index 407c1dbead9acb2d4f5cc7bcf09e0ffb5581287d..81f529d5131f295c80b23780dd0a0909a1fbdcf5 100644
--- a/base/message_pump_io_ios.h
+++ b/base/message_pump_io_ios.h
@@ -8,6 +8,7 @@
 #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"
 
@@ -81,7 +82,7 @@ class BASE_EXPORT MessagePumpIOSForIO : public MessagePumpNSRunLoop {
     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);