Add more components_unittests to GN build

components/translate/core/language_detection/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/features.gni")
 
-static_library("language_detection") {
+source_set("language_detection") {
   sources = [
     "language_detection_util.cc",
     "language_detection_util.h",
   ]
 
   deps = [
     "//base",
     "//components/translate/core/common",
     "//url",
   ]
 
   if (cld_version == 1) {
     deps += [ "//third_party/cld" ]
-  }
-  if (cld_version == 2) {
-    deps += [ "//third_party/cld_2" ]
+  } else if (cld_version == 2) {
+    deps += [ "//third_party/cld_2:cld2_platform_impl" ]
+  } else {
+    assert(false, "Need a CLD version")
   }
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "language_detection_util_unittest.cc",
+  ]
+  deps = [
+    ":language_detection",
+    "//testing/gtest",
+  ]
+}