Fix implicit access to raw pointer of scoped_refptr.

mojo/edk/system/shared_buffer_dispatcher.cc

 // Copyright 2014 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.
 
 #include "mojo/edk/system/shared_buffer_dispatcher.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <limits>
@@ skipping 258 matching lines @@
     return false;
   }
   handles[0] = handle_for_transit_.get();
   return true;
 }
 
 bool SharedBufferDispatcher::BeginTransit() {
   base::AutoLock lock(lock_);
   if (in_transit_)
     return false;
-  in_transit_ = shared_buffer_ != nullptr;
+  in_transit_ = static_cast<bool>(shared_buffer_);
   return in_transit_;
 }
 
 void SharedBufferDispatcher::CompleteTransitAndClose() {
   base::AutoLock lock(lock_);
   in_transit_ = false;
   shared_buffer_ = nullptr;
   ignore_result(handle_for_transit_.release());
 }
 
@@ skipping 40 matching lines @@
 
   // Checks for fields beyond |flags|:
 
   // (Nothing here yet.)
 
   return MOJO_RESULT_OK;
 }
 
 }  // namespace edk
 }  // namespace mojo