[CrOS Tether] Create proto_test_util.cc/h and move CreateTestDeviceStatus() there.

chromeos/components/tether/BUILD.gn

 # 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.
 
 assert(is_chromeos, "Non-ChromeOS builds cannot depend on //chromeos")
 
 static_library("tether") {
   sources = [
     "active_host.cc",
     "active_host.h",
@@ skipping 98 matching lines @@
     "fake_tether_host_fetcher.cc",
     "fake_tether_host_fetcher.h",
     "fake_wifi_hotspot_connector.cc",
     "fake_wifi_hotspot_connector.h",
     "mock_host_scan_device_prioritizer.cc",
     "mock_host_scan_device_prioritizer.h",
     "mock_local_device_data_provider.cc",
     "mock_local_device_data_provider.h",
     "mock_tether_host_response_recorder.cc",
     "mock_tether_host_response_recorder.h",
+    "proto_test_util.cc",
+    "proto_test_util.h",
   ]
 
   public_deps = [
     ":tether",
   ]
 
   deps = [
     "//base",
     "//chromeos",
+    "//chromeos/components/tether/proto",
     "//components/cryptauth",
     "//testing/gmock",
     "//testing/gtest",
     "//ui/message_center:test_support",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
 
@@ skipping 40 matching lines @@
     "//components/cryptauth/ble",
     "//components/prefs:test_support",
     "//components/signin/core/browser:test_support",
     "//device/bluetooth",
     "//device/bluetooth:mocks",
     "//testing/gmock",
     "//testing/gtest",
     "//ui/message_center:test_support",
   ]
 }