Make the fuchsia mojo/public repo the source of truth.

mojo/public/platform/native/mgl_onscreen_thunks.c

-// 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/public/platform/native/mgl_onscreen_thunks.h"
-
-#include <assert.h>
-
-#include "mojo/public/platform/native/thunk_export.h"
-
-static struct MGLOnscreenThunks g_onscreen_thunks = {0};
-
-void MGLResizeSurface(uint32_t width, uint32_t height) {
-  assert(g_onscreen_thunks.MGLResizeSurface);
-  g_onscreen_thunks.MGLResizeSurface(width, height);
-}
-
-void MGLSwapBuffers(void) {
-  assert(g_onscreen_thunks.MGLSwapBuffers);
-  g_onscreen_thunks.MGLSwapBuffers();
-}
-
-THUNK_EXPORT size_t MojoSetMGLOnscreenThunks(
-    const struct MGLOnscreenThunks* mgl_onscreen_thunks) {
-  if (mgl_onscreen_thunks->size >= sizeof(g_onscreen_thunks))
-    g_onscreen_thunks = *mgl_onscreen_thunks;
-  return sizeof(g_onscreen_thunks);
-}