Remove implicit conversions from scoped_refptr to T* in mojo/

mojo/system/message_pipe_dispatcher.cc

Index: mojo/system/message_pipe_dispatcher.cc
diff --git a/mojo/system/message_pipe_dispatcher.cc b/mojo/system/message_pipe_dispatcher.cc
index 3f08fd6658155830711ed4ef46028f7442237d1b..dac0d3038151ad6381fc17f22be1a8996c9ba1fa 100644
--- a/mojo/system/message_pipe_dispatcher.cc
+++ b/mojo/system/message_pipe_dispatcher.cc
@@ -70,7 +70,7 @@ MojoResult MessagePipeDispatcher::ValidateCreateOptions(
 
 void MessagePipeDispatcher::Init(scoped_refptr<MessagePipe> message_pipe,
                                  unsigned port) {
-  DCHECK(message_pipe);
+  DCHECK(message_pipe.get());
   DCHECK(port == 0 || port == 1);
 
   message_pipe_ = message_pipe;
@@ -140,7 +140,7 @@ scoped_refptr<MessagePipeDispatcher> MessagePipeDispatcher::Deserialize(
 
 MessagePipeDispatcher::~MessagePipeDispatcher() {
   // |Close()|/|CloseImplNoLock()| should have taken care of the pipe.
-  DCHECK(!message_pipe_);
+  DCHECK(!message_pipe_.get());
 }
 
 MessagePipe* MessagePipeDispatcher::GetMessagePipeNoLock() const {