[mojo-edk] Expose portable API for platform handle wrapping

mojo/platform_handle/platform_handle_private_thunks.cc

-// 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.
-
-#include "mojo/platform_handle/platform_handle_private_thunks.h"
-
-#include <assert.h>
-#include <stddef.h>
-
-#if defined(WIN32)
-#define THUNK_EXPORT __declspec(dllexport)
-#else
-#define THUNK_EXPORT __attribute__((visibility("default")))
-#endif
-
-extern "C" {
-
-static MojoPlatformHandlePrivateThunks g_thunks = {0};
-
-MojoResult MojoCreatePlatformHandleWrapper(MojoPlatformHandle platform_handle,
-                                           MojoHandle* wrapper) {
-  assert(g_thunks.CreatePlatformHandleWrapper);
-  return g_thunks.CreatePlatformHandleWrapper(platform_handle, wrapper);
-}
-
-MojoResult MojoExtractPlatformHandle(MojoHandle wrapper,
-                                     MojoPlatformHandle* platform_handle) {
-  assert(g_thunks.ExtractPlatformHandle);
-  return g_thunks.ExtractPlatformHandle(wrapper, platform_handle);
-}
-
-extern "C" THUNK_EXPORT size_t MojoSetPlatformHandlePrivateThunks(
-    const MojoPlatformHandlePrivateThunks* thunks) {
-  if (thunks->size >= sizeof(g_thunks))
-    g_thunks = *thunks;
-  return sizeof(g_thunks);
-}
-
-}  // extern "C"