TaskManager: use an unordered_map for tracking network usage

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 3594 matching lines @@
       "../browser/signin/mutable_profile_oauth2_token_service_delegate_unittest.cc",
       "../browser/speech/extension_api/extension_manifests_tts_unittest.cc",
       "../browser/speech/tts_controller_unittest.cc",
       "../browser/sync/sessions/browser_list_router_helper_unittest.cc",
       "../browser/sync/sync_ui_util_unittest.cc",  # Sync setup uses native ui.
       "../browser/task_manager/providers/browser_process_task_unittest.cc",
       "../browser/task_manager/providers/child_process_task_unittest.cc",
       "../browser/task_manager/sampling/shared_sampler_win_unittest.cc",
       "../browser/task_manager/sampling/task_group_unittest.cc",
       "../browser/task_manager/sampling/task_manager_impl_unittest.cc",
+      "../browser/task_manager/sampling/task_manager_io_thread_helper_unittest.cc",
       "../browser/task_manager/task_manager_observer_unittest.cc",
       "../browser/task_manager/test_task_manager.cc",
       "../browser/task_manager/test_task_manager.h",
       "../browser/themes/browser_theme_pack_unittest.cc",
       "../browser/themes/theme_properties_unittest.cc",
       "../browser/themes/theme_service_unittest.cc",
       "../browser/themes/theme_syncable_service_unittest.cc",
       "../browser/translate/translate_manager_render_view_host_unittest.cc",
       "../browser/ui/webui/theme_source_unittest.cc",
 
@@ skipping 1553 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }