Fix broken clockstate.network2 histogram and add unit test

components/network_time/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.
 
 static_library("network_time") {
   sources = [
     "network_time_pref_names.cc",
     "network_time_pref_names.h",
     "network_time_tracker.cc",
     "network_time_tracker.h",
@@ skipping 10 matching lines @@
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "network_time_tracker_unittest.cc",
   ]
 
   deps = [
     ":network_time",
+    ":network_time_test_support",
     "//base",
     "//base/test:test_support",
     "//components/client_update_protocol",
     "//components/prefs:test_support",
     "//components/variations",
     "//net",
     "//net:test_support",
     "//testing/gtest",
   ]
 }
+
+source_set("network_time_test_support") {
+  testonly = true
+  sources = [
+    "network_time_test_utils.cc",
+    "network_time_test_utils.h",
+  ]
+
+  deps = [
+    "//base",
+    "//base/test:test_support",
+    "//components/variations",
+    "//testing/gtest",
+  ]
+}