chrome: Cleanup class/struct forward declarations

chrome/browser/metrics/chrome_metrics_service_client.h

 // 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.
 
 #ifndef CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_CLIENT_H_
 #define CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_CLIENT_H_
 
 #include <stdint.h>
 
 #include <deque>
@@ skipping 13 matching lines @@
 #include "components/omnibox/browser/omnibox_event_global_tracker.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ppapi/features/features.h"
 
 class AntiVirusMetricsProvider;
 class ChromeOSMetricsProvider;
 class GoogleUpdateMetricsProviderWin;
 class PluginMetricsProvider;
 class PrefRegistrySimple;
-class PrefService;
-
-#if !defined(OS_CHROMEOS)
-class SigninStatusMetricsProvider;
-#endif
 
 namespace browser_watcher {
 class WatcherMetricsProviderWin;
 }  // namespace browser_watcher
 
 namespace metrics {
 class DriveMetricsProvider;
 class MetricsService;
 class MetricsStateManager;
 class ProfilerMetricsProvider;
@@ skipping 174 matching lines @@
   // Whether this client has already uploaded profiler data during this session.
   // Profiler data is uploaded at most once per session.
   bool has_uploaded_profiler_data_;
 
   base::WeakPtrFactory<ChromeMetricsServiceClient> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeMetricsServiceClient);
 };
 
 #endif  // CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_CLIENT_H_