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

mojo/public/c/tests/compile/pure_cpp.cc

-// Copyright 2016 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.
-
-// This file is used to ensure that our C headers can be compiled as C++ with
-// more stringent warnings, in particular with "-Wundef".
-
-// Include all the header files that are meant to be compilable as C.
-#include <mojo/environment/async_waiter.h>
-#include <mojo/environment/logger.h>
-#include <mojo/macros.h>
-#include <mojo/result.h>
-#include <mojo/system/buffer.h>
-#include <mojo/system/data_pipe.h>
-#include <mojo/system/handle.h>
-#include <mojo/system/main.h>
-#include <mojo/system/message_pipe.h>
-#include <mojo/system/time.h>
-#include <mojo/system/wait.h>
-#include <mojo/system/wait_set.h>
-
-// We don't actually want to test anything; we just want to make sure that this
-// file is compiled/linked in (this function is called from core_unittest.cc).
-const char* MinimalCppTest() {
-  return nullptr;
-}