Support read-only duplicates of Mojo shared buffers.

mojo/edk/system/data_pipe_producer_dispatcher.cc

 // 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.
 
 #include "mojo/edk/system/data_pipe_producer_dispatcher.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 367 matching lines @@
   NodeController* node_controller = internal::g_core->GetNodeController();
   ports::PortRef port;
   if (node_controller->node()->GetPort(ports[0], &port) != ports::OK)
     return nullptr;
 
   PlatformHandle buffer_handle;
   std::swap(buffer_handle, handles[0]);
   scoped_refptr<PlatformSharedBuffer> ring_buffer =
       PlatformSharedBuffer::CreateFromPlatformHandle(
           state->options.capacity_num_bytes,
+          false /* read_only */,
           ScopedPlatformHandle(buffer_handle));
   if (!ring_buffer) {
     DLOG(ERROR) << "Failed to deserialize shared buffer handle.";
     return nullptr;
   }
 
   scoped_refptr<DataPipeProducerDispatcher> dispatcher =
       new DataPipeProducerDispatcher(node_controller, port, ring_buffer,
                                      state->options, false /* initialized */,
                                      state->pipe_id);
@@ skipping 141 matching lines @@
   }
 
   if (peer_closed_ != was_peer_closed ||
       available_capacity_ != previous_capacity) {
     awakable_list_.AwakeForStateChange(GetHandleSignalsStateNoLock());
   }
 }
 
 }  // namespace edk
 }  // namespace mojo