Add translate client mock.

components/translate/core/browser/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("//build/config/ui.gni")
 
 static_library("browser") {
   sources = [
     "language_model.cc",
     "language_model.h",
@@ skipping 76 matching lines @@
       "options_menu_model.h",
     ]
   }
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "language_model_unittest.cc",
     "language_state_unittest.cc",
+    "mock_translate_client.cc",
+    "mock_translate_client.h",
     "mock_translate_driver.cc",
     "mock_translate_driver.h",
     "mock_translate_ranker.cc",
     "mock_translate_ranker.h",
     "ranker_model_loader_unittest.cc",
     "ranker_model_unittest.cc",
     "translate_browser_metrics_unittest.cc",
     "translate_language_list_unittest.cc",
     "translate_manager_unittest.cc",
     "translate_prefs_unittest.cc",
@@ skipping 12 matching lines @@
     "//components/sync_preferences:test_support",
     "//components/translate/core/browser/proto",
     "//components/translate/core/common",
     "//components/ukm",
     "//components/ukm:test_support",
     "//components/variations",
     "//net:test_support",
     "//testing/gtest",
   ]
 }