UKM: Added support for navigation sources

components/ukm/BUILD.gn

 # Copyright 2017 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("//testing/test.gni")
 
 # The Url-Keyed Metrics (UKM) service is responsible for gathering and
 # uploading reports that contain fine grained performance metrics including
 # URLs for top-level navigations.
 static_library("ukm") {
   sources = [
     "metrics_reporting_scheduler.cc",
     "metrics_reporting_scheduler.h",
     "persisted_logs_metrics_impl.cc",
     "persisted_logs_metrics_impl.h",
     "ukm_pref_names.cc",
     "ukm_pref_names.h",
     "ukm_service.cc",
     "ukm_service.h",
+    "ukm_source.cc",
+    "ukm_source.h",
   ]
 
   deps = [
     "//base",
     "//components/data_use_measurement/core",
     "//components/metrics",
     "//components/prefs",
     "//components/variations",
   ]
 }
 
 # Helper library for observing signals that we need to clear any local data.
 static_library("observers") {
   sources = [
     "observers/history_delete_observer.cc",
     "observers/history_delete_observer.h",
   ]
 
   deps = [
     "//base",
     "//components/history/core/browser",
   ]
 }
 
+static_library("test_support") {
+  testonly = true
+  sources = [
+    "test_ukm_service.cc",
+    "test_ukm_service.h",
+  ]
+
+  public_deps = [
+    ":ukm",
+  ]
+  deps = [
+    "//base",
+    "//components/metrics:test_support",
+    "//components/prefs:test_support",
+  ]
+}
+
 source_set("unit_tests") {
   testonly = true
   sources = [
     "ukm_service_unittest.cc",
   ]
 
   deps = [
+    ":test_support",
     ":ukm",
     "//base",
     "//base/test:test_support",
     "//components/metrics",
     "//components/metrics:test_support",
     "//components/prefs:test_support",
     "//net:test_support",
     "//testing/gtest",
     "//url",
   ]
 }
 
 # Convenience testing target
 test("ukm_unittests") {
   deps = [
     ":unit_tests",
     "//base",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
   ]
 }