Add metrics to keep track of the tab activate/deactivate cycle

chrome/chrome_browser.gypi

 # Copyright 2012 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.
 
 {
   'variables': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 2176 matching lines @@
       'browser/metrics/chrome_metrics_service_accessor.cc',
       'browser/metrics/chrome_metrics_service_accessor.h',
       'browser/metrics/chrome_metrics_service_client.cc',
       'browser/metrics/chrome_metrics_service_client.h',
       'browser/metrics/chrome_metrics_services_manager_client.cc',
       'browser/metrics/chrome_metrics_services_manager_client.h',
       'browser/metrics/chrome_stability_metrics_provider.cc',
       'browser/metrics/chrome_stability_metrics_provider.h',
       'browser/metrics/field_trial_synchronizer.cc',
       'browser/metrics/field_trial_synchronizer.h',
+      'browser/metrics/google_update_metrics_provider_win.cc',
+      'browser/metrics/google_update_metrics_provider_win.h',
       'browser/metrics/https_engagement_metrics_provider.cc',
       'browser/metrics/https_engagement_metrics_provider.h',
-      'browser/metrics/google_update_metrics_provider_win.cc',
-      'browser/metrics/google_update_metrics_provider_win.h',
       'browser/metrics/jumplist_metrics_win.cc',
       'browser/metrics/jumplist_metrics_win.h',
       'browser/metrics/metrics_memory_details.cc',
       'browser/metrics/metrics_memory_details.h',
       'browser/metrics/metrics_reporting_state.cc',
       'browser/metrics/metrics_reporting_state.h',
       'browser/metrics/perf/perf_provider_chromeos.cc',
       'browser/metrics/perf/perf_provider_chromeos.h',
       'browser/metrics/sampling_metrics_provider.cc',
       'browser/metrics/sampling_metrics_provider.h',
       'browser/metrics/subprocess_metrics_provider.cc',
       'browser/metrics/subprocess_metrics_provider.h',
+      'browser/metrics/tab_usage_recorder.cc',
+      'browser/metrics/tab_usage_recorder.h',
       'browser/metrics/thread_watcher.cc',
       'browser/metrics/thread_watcher.h',
       'browser/metrics/thread_watcher_android.cc',
       'browser/metrics/thread_watcher_android.h',
       'browser/metrics/thread_watcher_report_hang.cc',
       'browser/metrics/thread_watcher_report_hang.h',
       'browser/metrics/time_ticks_experiment_win.cc',
       'browser/metrics/time_ticks_experiment_win.h',
       'browser/metrics/variations/chrome_variations_service_client.cc',
       'browser/metrics/variations/chrome_variations_service_client.h',
@@ skipping 2134 matching lines @@
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
             'common',
           ],
         },
       ],
     }],
   ],
 }