Remove MetricsServiceObserver in favor of MetricsProvider.

components/metrics.gypi

 # 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.
 
 {
   'targets': [
     {
       # GN version: //components/metrics
       'target_name': 'metrics',
       'type': 'static_library',
@@ skipping 25 matching lines @@
         'metrics/metrics_log_uploader.cc',
         'metrics/metrics_log_uploader.h',
         'metrics/metrics_pref_names.cc',
         'metrics/metrics_pref_names.h',
         'metrics/metrics_provider.h',
         'metrics/metrics_reporting_scheduler.cc',
         'metrics/metrics_reporting_scheduler.h',
         'metrics/metrics_service.cc',
         'metrics/metrics_service.h',
         'metrics/metrics_service_client.h',
-        'metrics/metrics_service_observer.cc',
-        'metrics/metrics_service_observer.h',
         'metrics/metrics_state_manager.cc',
         'metrics/metrics_state_manager.h',
         'metrics/metrics_switches.cc',
         'metrics/metrics_switches.h',
         'metrics/persisted_logs.cc',
         'metrics/persisted_logs.h',
       ],
       'conditions': [
         ['chromeos==1', {
           'dependencies': [
@@ skipping 81 matching lines @@
             'metrics/serialization/metric_sample.h',
           ],
           'dependencies': [
             '../base/base.gyp:base',
           ],
         },
       ],
     }],
   ],
 }