Mojo: Add a "GetType()" to Dispatchers.

mojo/system/data_pipe_producer_dispatcher.cc

Index: mojo/system/data_pipe_producer_dispatcher.cc
diff --git a/mojo/system/data_pipe_producer_dispatcher.cc b/mojo/system/data_pipe_producer_dispatcher.cc
index 2943b6607a3147479d1d7223da92c8c10b7b491d..c5b8e9f7d024d6d78841627e115134286f9023c0 100644
--- a/mojo/system/data_pipe_producer_dispatcher.cc
+++ b/mojo/system/data_pipe_producer_dispatcher.cc
@@ -19,6 +19,10 @@ void DataPipeProducerDispatcher::Init(scoped_refptr<DataPipe> data_pipe) {
   data_pipe_ = data_pipe;
 }
 
+Dispatcher::Type DataPipeProducerDispatcher::GetType() {
+  return kTypeDataPipeProducer;
+}
+
 DataPipeProducerDispatcher::~DataPipeProducerDispatcher() {
   // |Close()|/|CloseImplNoLock()| should have taken care of the pipe.
   DCHECK(!data_pipe_.get());