Remove implicit conversions from scoped_refptr to T* in mojo/

mojo/system/message_pipe.cc

Index: mojo/system/message_pipe.cc
diff --git a/mojo/system/message_pipe.cc b/mojo/system/message_pipe.cc
index efb8c6711b0b218384445fd02f511dcb0525513d..1b4ecfb8e59160d67d358cb367ce16a4a34baab3 100644
--- a/mojo/system/message_pipe.cc
+++ b/mojo/system/message_pipe.cc
@@ -162,7 +162,7 @@ bool MessagePipe::Attach(unsigned port,
                          scoped_refptr<Channel> channel,
                          MessageInTransit::EndpointId local_id) {
   DCHECK(port == 0 || port == 1);
-  DCHECK(channel);
+  DCHECK(channel.get());
   DCHECK_NE(local_id, MessageInTransit::kInvalidEndpointId);
 
   base::AutoLock locker(lock_);