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

mojo/edk/system/master.mojom

Index: mojo/edk/system/master.mojom
diff --git a/mojo/edk/system/master.mojom b/mojo/edk/system/master.mojom
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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.
+
+module mojo;
+
+interface Master {
+  // These methods are only called on Windows.
+  HandleToToken(handle platform_handle) => (int32 result, uint64 token);
+  TokenToHandle(uint64 token) => (int32 result, handle platform_handle);
+};