Add a Mojo EDK for Chrome that uses one OS pipe per message pipe.

mojo/edk/system/data_pipe.h

Index: mojo/edk/system/data_pipe.h
diff --git a/mojo/edk/system/data_pipe.h b/mojo/edk/system/data_pipe.h
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+// Copyright 2015 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_EDK_SYSTEM_DATA_PIPE_H_
+#define MOJO_EDK_SYSTEM_DATA_PIPE_H_
+
+#include "base/compiler_specific.h"
+#include "mojo/edk/embedder/platform_handle_vector.h"
+#include "mojo/edk/embedder/scoped_platform_handle.h"
+#include "mojo/edk/system/system_impl_export.h"
+#include "mojo/public/c/system/data_pipe.h"
+#include "mojo/public/c/system/types.h"
+#include "mojo/public/cpp/system/macros.h"
+
+namespace mojo {
+namespace edk {
+class RawChannel;
+
+// Shared code between DataPipeConsumerDispatcher and
+// DataPipeProducerDispatcher.
+class MOJO_SYSTEM_IMPL_EXPORT DataPipe {
+ public:
+  // The default options for |MojoCreateDataPipe()|. (Real uses should obtain
+  // this via |ValidateCreateOptions()| with a null |in_options|; this is
+  // exposed directly for testing convenience.)
+  static MojoCreateDataPipeOptions GetDefaultCreateOptions();
+
+  // Validates and/or sets default options for |MojoCreateDataPipeOptions|. If
+  // non-null, |in_options| must point to a struct of at least
+  // |in_options->struct_size| bytes. |out_options| must point to a (current)
+  // |MojoCreateDataPipeOptions| and will be entirely overwritten on success (it
+  // may be partly overwritten on failure).
+  static MojoResult ValidateCreateOptions(
+      const MojoCreateDataPipeOptions* in_options,
+      MojoCreateDataPipeOptions* out_options);
+
+  // Helper methods used by DataPipeConsumerDispatcher and
+  // DataPipeProducerDispatcher for serialization and deserialization.
+  static void StartSerialize(bool have_channel_handle,
+                             bool have_shared_memory,
+                             size_t* max_size,
+                             size_t* max_platform_handles);
+  static void EndSerialize(const MojoCreateDataPipeOptions& options,
+                           ScopedPlatformHandle channel_handle,
+                           ScopedPlatformHandle shared_memory_handle,
+                           size_t shared_memory_size,
+                           void* destination,
+                           size_t* actual_size,
+                           PlatformHandleVector* platform_handles);
+  static ScopedPlatformHandle Deserialize(
+      const void* source,
+      size_t size,
+      PlatformHandleVector* platform_handles,
+      MojoCreateDataPipeOptions* options,
+      ScopedPlatformHandle* shared_memory_handle,
+      size_t* shared_memory_size);
+};
+
+}  // namespace edk
+}  // namespace mojo
+
+#endif  // MOJO_EDK_SYSTEM_DATA_PIPE_H_