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

mojo/public/c/include/mojo/bindings/string.h

-// 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.
-
-#ifndef MOJO_PUBLIC_C_INCLUDE_MOJO_BINDINGS_STRING_H_
-#define MOJO_PUBLIC_C_INCLUDE_MOJO_BINDINGS_STRING_H_
-
-#include <mojo/bindings/array.h>
-#include <mojo/bindings/buffer.h>
-
-// A mojom string is a mojom array of UTF-8 chars that need not be
-// null-terminated.
-struct MojomStringHeader {
-  struct MojomArrayHeader chars;
-};
-MOJO_STATIC_ASSERT(sizeof(struct MojomStringHeader) ==
-                       sizeof(struct MojomArrayHeader),
-                   "MojomStringHeader must be just a MojomArrayHeader.");
-
-union MojomStringHeaderPtr {
-  struct MojomStringHeader* ptr;
-  uint64_t offset;
-};
-MOJO_STATIC_ASSERT(sizeof(union MojomStringHeaderPtr) == 8,
-                   "MojomStringHeaderPtr must be 8 byes.");
-
-#endif  // MOJO_PUBLIC_C_INCLUDE_MOJO_BINDINGS_STRING_H_