Add our own (mojo::util::)ScopedFILE and replace uses of base::ScopedFILE with it.

mojo/edk/embedder/BUILD.gn

 # Copyright 2014 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.
 
 import("../mojo_edk.gni")
 
 mojo_edk_source_set("embedder") {
   # This isn't really a standalone target; it must be linked into the
   # mojo_system_impl component.
   mojo_edk_visibility = [ "mojo/edk/system" ]
@@ skipping 77 matching lines @@
 
   mojo_sdk_public_deps = [ "mojo/public/cpp/system" ]
 
   deps = [
     "//base",
   ]
 
   if (is_android) {
     deps += [ "//third_party/ashmem" ]
   }
+
+  mojo_edk_deps = [ "mojo/edk/util" ]
 }
 
 mojo_edk_source_set("delegates") {
   # This isn't really a standalone target; it must be linked into the
   # mojo_system_impl component.
   visibility = [ ":embedder" ]
 
   mojo_edk_visibility = [ "mojo/edk/system" ]
 
   sources = [
@@ skipping 24 matching lines @@
   deps = [
     "//base",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 
   mojo_edk_deps = [
     "mojo/edk/test:test_support",
     "mojo/edk/system",
     "mojo/edk/system:test_utils",
+    "mojo/edk/util",
   ]
 }