Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

base/test/BUILD.gn

 # Copyright (c) 2013 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/ui.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 source_set("test_support") {
   sources = [
     "expectations/expectation.cc",
     "expectations/expectation.h",
     "expectations/parser.cc",
     "expectations/parser.h",
     "gtest_xml_util.cc",
     "gtest_xml_util.h",
+    "histogram_tester.cc",
+    "histogram_tester.h",
     "launcher/test_launcher.cc",
     "launcher/test_launcher.h",
     "launcher/test_result.cc",
     "launcher/test_result.h",
     "launcher/test_results_tracker.cc",
     "launcher/test_results_tracker.h",
     "launcher/unit_test_launcher.cc",
     "launcher/unit_test_launcher.h",
     "launcher/unit_test_launcher_ios.cc",
     "mock_chrome_application_mac.h",
@@ skipping 20 matching lines @@
     "scoped_path_override.cc",
     "scoped_path_override.h",
     "sequenced_task_runner_test_template.cc",
     "sequenced_task_runner_test_template.h",
     "sequenced_worker_pool_owner.cc",
     "sequenced_worker_pool_owner.h",
     "simple_test_clock.cc",
     "simple_test_clock.h",
     "simple_test_tick_clock.cc",
     "simple_test_tick_clock.h",
-    "statistics_delta_reader.cc",
-    "statistics_delta_reader.h",
     "task_runner_test_template.cc",
     "task_runner_test_template.h",
     "test_file_util.cc",
     "test_file_util.h",
     "test_file_util_android.cc",
     "test_file_util_linux.cc",
     "test_file_util_mac.cc",
     "test_file_util_posix.cc",
     "test_file_util_win.cc",
     "test_listener_ios.h",
@@ skipping 83 matching lines @@
 }
 
 if (is_android) {
   generate_jni("base_unittests_jni_headers") {
     sources = [
       "android/java/src/org/chromium/base/ContentUriTestUtils.java",
     ]
     jni_package = "base"
   }
 }