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

mojo/public/c/include/MGL/mgl_echo.h

Index: mojo/public/c/include/MGL/mgl_echo.h
diff --git a/mojo/public/c/include/MGL/mgl_echo.h b/mojo/public/c/include/MGL/mgl_echo.h
deleted file mode 100644
index e78c4274502f3fb79b5e0786054d444927dace93..0000000000000000000000000000000000000000
--- a/mojo/public/c/include/MGL/mgl_echo.h
+++ /dev/null
@@ -1,22 +0,0 @@
-// 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.
-
-// Note: This header should be compilable as C.
-
-#ifndef MOJO_PUBLIC_C_INCLUDE_MGL_MGL_ECHO_H_
-#define MOJO_PUBLIC_C_INCLUDE_MGL_MGL_ECHO_H_
-
-#include <MGL/mgl_types.h>
-#include <mojo/macros.h>
-#include <stdint.h>
-
-MOJO_BEGIN_EXTERN_C
-
-typedef void (*MGLEchoCallback)(void* closure);
-
-void MGLEcho(MGLEchoCallback callback, void* closure);
-
-MOJO_END_EXTERN_C
-
-#endif  // MOJO_PUBLIC_C_INCLUDE_MGL_MGL_ECHO_H_