Add more components_unittests to GN build

components/translate/core/common/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.
 
 source_set("common") {
   sources = [
     "language_detection_details.cc",
     "language_detection_details.h",
     "translate_constants.cc",
     "translate_constants.h",
     "translate_errors.h",
     "translate_metrics.cc",
     "translate_metrics.h",
     "translate_pref_names.cc",
     "translate_pref_names.h",
     "translate_switches.cc",
     "translate_switches.h",
     "translate_util.cc",
     "translate_util.h",
   ]
 
   deps = [
     "//base",
     "//url",
   ]
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "translate_metrics_unittest.cc",
+    "translate_util_unittest.cc",
+  ]
+  deps = [
+    ":common",
+    "//testing/gtest",
+  ]
+}