Cleanup: Remove unneeded forward declarations from various chrome/browser subdirectories.

chrome/browser/metrics/metrics_service.h

 // Copyright (c) 2011 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.
 
 // This file defines a service that collects information about the user
 // experience in order to help improve future versions of the app.
 
 #ifndef CHROME_BROWSER_METRICS_METRICS_SERVICE_H_
 #define CHROME_BROWSER_METRICS_METRICS_SERVICE_H_
 #pragma once
@@ skipping 12 matching lines @@
 #include "content/public/common/url_fetcher_delegate.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/external_metrics.h"
 #endif
 
 class BookmarkModel;
 class BookmarkNode;
-class HistogramSynchronizer;
-class MetricsLogBase;
 class MetricsReportingScheduler;
 class PrefService;
 class Profile;
 class RenderProcessHost;
 class TemplateURLService;
 
 namespace base {
 class DictionaryValue;
 class MessageLoopProxy;
 }
@@ skipping 359 matching lines @@
   friend class InstantFieldTrial;
   friend bool prerender::IsOmniboxEnabled(Profile* profile);
 
   // Returns true if prefs::kMetricsReportingEnabled is set.
   static bool IsMetricsReportingEnabled();
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(MetricsServiceHelper);
 };
 
 #endif  // CHROME_BROWSER_METRICS_METRICS_SERVICE_H_