Add desktop engagement metrics.

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 1113 matching lines @@
       'browser/metrics/perf/random_selector.h',
       'browser/metrics/perf/windowed_incognito_observer.cc',
       'browser/metrics/perf/windowed_incognito_observer.h',
       # This is technically also dependent on enable_plugins but we don't
       # support ChromeOS with enable_plugins==0.
       'browser/renderer_host/pepper/pepper_platform_verification_message_filter.cc',
       'browser/renderer_host/pepper/pepper_platform_verification_message_filter.h',
     ],
     # Everything but Android, iOS, and CrOS.
     'chrome_browser_desktop_sources': [
+      'browser/metrics/desktop_engagement/audible_contents_tracker.cc',
+      'browser/metrics/desktop_engagement/audible_contents_tracker.h',
+      'browser/metrics/desktop_engagement/chrome_visibility_observer.cc',
+      'browser/metrics/desktop_engagement/chrome_visibility_observer.h',
+      'browser/metrics/desktop_engagement/desktop_engagement_observer.cc',
+      'browser/metrics/desktop_engagement/desktop_engagement_observer.h',
+      'browser/metrics/desktop_engagement/desktop_engagement_service.cc',
+      'browser/metrics/desktop_engagement/desktop_engagement_service.h',
       'browser/platform_util.cc',
       'browser/policy/cloud/user_policy_signin_service.cc',
       'browser/policy/cloud/user_policy_signin_service.h',
       'browser/profiles/avatar_menu_actions_desktop.cc',
       'browser/profiles/avatar_menu_actions_desktop.h',
       'browser/profiles/avatar_menu_desktop.cc',
       'browser/profiles/avatar_menu_observer.h',
       'browser/profiles/profile_list_desktop.cc',
       'browser/profiles/profile_list_desktop.h',
       'browser/profiles/profile_statistics.cc',
@@ skipping 3213 matching lines @@
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
             'common',
           ],
         },
       ],
     }],
   ],
 }