Split mojo_system dylib into public and private

mojo/system/message_pipe_endpoint.h

Index: mojo/system/message_pipe_endpoint.h
diff --git a/mojo/system/message_pipe_endpoint.h b/mojo/system/message_pipe_endpoint.h
index 2939c935d4c095bb2dd9977ba056cd0bb84b40f9..70175967fbb77f79dd208dd355547373e331ca97 100644
--- a/mojo/system/message_pipe_endpoint.h
+++ b/mojo/system/message_pipe_endpoint.h
@@ -12,8 +12,8 @@
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "mojo/public/system/core.h"
-#include "mojo/public/system/system_export.h"
 #include "mojo/system/message_in_transit.h"
+#include "mojo/system/system_impl_export.h"
 
 namespace mojo {
 namespace system {
@@ -30,7 +30,7 @@ class Waiter;
 // |MessagePipeEndpoint| also implements the functionality required by the
 // dispatcher, e.g., to read messages and to wait. Implementations of this class
 // are not thread-safe; instances are protected by |MesssagePipe|'s lock.
-class MOJO_SYSTEM_EXPORT MessagePipeEndpoint {
+class MOJO_SYSTEM_IMPL_EXPORT MessagePipeEndpoint {
  public:
   virtual ~MessagePipeEndpoint() {}