[TabMetrics] Add signals that mark the start and end of session restore.

chrome/test/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/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
@@ skipping 3234 matching lines @@
     # TODO(hashimoto): those tests should be componentized and moved to
     # //components:components_unittests, http://crbug.com/527882.
     "../browser/search_engines/template_url_fetcher_unittest.cc",
     "../browser/search_engines/template_url_parser_unittest.cc",
     "../browser/search_engines/template_url_service_sync_unittest.cc",
     "../browser/search_engines/template_url_service_unittest.cc",
     "../browser/service_process/service_process_control_mac_unittest.mm",
     "../browser/sessions/chrome_serialized_navigation_driver_unittest.cc",
     "../browser/sessions/restore_on_startup_policy_handler_unittest.cc",
     "../browser/sessions/session_common_utils_unittest.cc",
+    "../browser/sessions/session_restore_observer_unittest.cc",
     "../browser/shell_integration_win_unittest.cc",
     "../browser/signin/account_reconcilor_unittest.cc",
     "../browser/signin/chrome_signin_client_unittest.cc",
     "../browser/signin/chrome_signin_status_metrics_provider_delegate_unittest.cc",
     "../browser/signin/local_auth_unittest.cc",
     "../browser/signin/signin_manager_unittest.cc",
     "../browser/signin/signin_status_metrics_provider_chromeos_unittest.cc",
     "../browser/signin/signin_tracker_unittest.cc",
     "../browser/signin/test_signin_client_builder.cc",
     "../browser/signin/test_signin_client_builder.h",
@@ skipping 1901 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }