Split mojo_system dylib into public and private

mojo/system/message_in_transit.h

 // Copyright 2013 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.
 
 #ifndef MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_
 #define MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_
 
 #include <stdint.h>
 #include <stdlib.h>  // For |free()|.
 
 #include "base/basictypes.h"
-#include "mojo/public/system/system_export.h"
+#include "mojo/system/system_impl_export.h"
 
 namespace mojo {
 namespace system {
 
 // This class is used to represent data in transit. It is thread-unsafe.
 // Note: This class is POD.
-class MOJO_SYSTEM_EXPORT MessageInTransit {
+class MOJO_SYSTEM_IMPL_EXPORT MessageInTransit {
  public:
   typedef uint16_t Type;
   // Messages that are forwarded to |MessagePipeEndpoint|s.
   static const Type kTypeMessagePipeEndpoint = 0;
   // Messages that are forwarded to |MessagePipe|s.
   static const Type kTypeMessagePipe = 1;
   // Messages that are consumed by the channel.
   static const Type TYPE_CHANNEL = 2;
 
   typedef uint16_t Subtype;
@@ skipping 75 matching lines @@
 };
 
 // The size of |MessageInTransit| must be appropriate to maintain alignment of
 // the following data.
 COMPILE_ASSERT(sizeof(MessageInTransit) == 16, MessageInTransit_has_wrong_size);
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_