Add more components tests to the GN build.

components/captive_portal/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.
 
 component("captive_portal") {
   sources = [
     "captive_portal_detector.cc",
     "captive_portal_detector.h",
     "captive_portal_types.cc",
     "captive_portal_types.h",
@@ skipping 15 matching lines @@
     "captive_portal_testing_utils.h",
   ]
 
   deps = [
     ":captive_portal",
     "//base",
     "//net",
     "//url",
   ]
 }
+
+source_set("unit_tests") {
+  sources = [
+    "captive_portal_detector_unittest.cc",
+  ]
+
+  deps = [
+    ":captive_portal",
+    "//testing/gtest",
+  ]
+}