Use ArcFileSystemInstance to access files on ARC.

components/arc/BUILD.gn

 # 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 static_library("arc") {
   sources = [
     "arc_bridge_host_impl.cc",
@@ skipping 167 matching lines @@
   testonly = true
   sources = [
     "test/fake_app_instance.cc",
     "test/fake_app_instance.h",
     "test/fake_arc_bridge_service.cc",
     "test/fake_arc_bridge_service.h",
     "test/fake_arc_session.cc",
     "test/fake_arc_session.h",
     "test/fake_bluetooth_instance.cc",
     "test/fake_bluetooth_instance.h",
+    "test/fake_file_system_instance.cc",
+    "test/fake_file_system_instance.h",
     "test/fake_intent_helper_instance.cc",
     "test/fake_intent_helper_instance.h",
     "test/fake_notifications_instance.cc",
     "test/fake_notifications_instance.h",
     "test/fake_policy_instance.cc",
     "test/fake_policy_instance.h",
   ]
 
   public_deps = [
     ":arc",
@@ skipping 31 matching lines @@
     "//testing/gtest",
     "//ui/aura",
     "//ui/aura:test_support",
     "//ui/base:test_support",
     "//ui/base/ime",
     "//ui/events",
     "//ui/events:dom_keycode_converter",
     "//url:url",
   ]
 }