Adds thunks for getting platform handles

mojo/platform_handle/platform_handle_exports.h

+// 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_PLATFORM_HANDLE_PLATFORM_HANDLE_EXPORTS_H_
+#define MOJO_PLATFORM_HANDLE_PLATFORM_HANDLE_EXPORTS_H_
+
+#if defined(COMPONENT_BUILD) && defined(MOJO_USE_SYSTEM_IMPL)
+#if defined(WIN32)
+
+#if defined(PLATFORM_HANDLE_IMPLEMENTATION)
+#define PLATFORM_HANDLE_EXPORT __declspec(dllexport)
+#else
+#define PLATFORM_HANDLE_EXPORT __declspec(dllimport)
+#endif
+
+#else  // !defined(WIN32)
+
+#if defined(PLATFORM_HANDLE_IMPLEMENTATION)
+#define PLATFORM_HANDLE_EXPORT __attribute__((visibility("default")))
+#else
+#define PLATFORM_HANDLE_EXPORT
+#endif
+
+#endif  // defined(WIN32)
+
+#else  // !defined(COMPONENT_BUILD) || !defined(MOJO_USE_SYSTEM_IMPL)
+
+#define PLATFORM_HANDLE_EXPORT
+
+#endif  // defined(COMPONENT_BUILD) && defined(MOJO_USE_SYSTEM_IMPL)
+
+#endif  // MOJO_PLATFORM_HANDLE_PLATFORM_HANDLE_EXPORTS_H_