[UMA] Use proper C++ objects to serialize tracked_objects across process boundaries.

chrome/chrome_browser.gypi

 # Copyright (c) 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.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 1342 matching lines @@
         'browser/memory_details_android.cc',
         'browser/memory_details_linux.cc',
         'browser/memory_details_mac.cc',
         'browser/memory_details_win.cc',
         'browser/memory_purger.cc',
         'browser/memory_purger.h',
         'browser/metrics/field_trial_synchronizer.cc',
         'browser/metrics/field_trial_synchronizer.h',
         'browser/metrics/histogram_synchronizer.cc',
         'browser/metrics/histogram_synchronizer.h',
-        'browser/metrics/tracking_synchronizer.cc',
-        'browser/metrics/tracking_synchronizer.h',
         'browser/metrics/metric_event_duration_details.h',
         'browser/metrics/metrics_log.cc',
         'browser/metrics/metrics_log.h',
         'browser/metrics/metrics_log_serializer.cc',
         'browser/metrics/metrics_log_serializer.h',
         'browser/metrics/metrics_reporting_scheduler.cc',
         'browser/metrics/metrics_reporting_scheduler.h',
         'browser/metrics/metrics_response.cc',
         'browser/metrics/metrics_response.h',
         'browser/metrics/metrics_service.cc',
         'browser/metrics/metrics_service.h',
         'browser/metrics/thread_watcher.cc',
         'browser/metrics/thread_watcher.h',
+        'browser/metrics/tracking_synchronizer.cc',
+        'browser/metrics/tracking_synchronizer.h',
+        'browser/metrics/tracking_synchronizer_observer.h',
         'browser/mock_keychain_mac.cc',
         'browser/mock_keychain_mac.h',
         'browser/native_window_notification_source.h',
         'browser/net/browser_url_util.cc',
         'browser/net/browser_url_util.h',
         'browser/net/chrome_cookie_notification_details.h',
         'browser/net/chrome_fraudulent_certificate_reporter.cc',
         'browser/net/chrome_fraudulent_certificate_reporter.h',
         'browser/net/chrome_net_log.cc',
         'browser/net/chrome_net_log.h',
@@ skipping 3991 matching lines @@
          'variables': {
           'proto_in_dir': '../third_party/cros_system_api/dbus/',
           'proto_out_dir': 'chrome/browser/chromeos/dbus',
          },
          'includes': ['../build/protoc.gypi'],
         }],
       ],
     },
   ],
 }