chrome: Cleanup class/struct forward declarations

chrome/browser/chrome_browser_main.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROME_BROWSER_MAIN_H_
 #define CHROME_BROWSER_CHROME_BROWSER_MAIN_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
 #include "base/profiler/stack_sampling_profiler.h"
 #include "base/tracked_objects.h"
 #include "build/build_config.h"
 #include "chrome/browser/chrome_browser_field_trials.h"
 #include "chrome/browser/chrome_process_singleton.h"
 #include "chrome/browser/first_run/first_run.h"
 #include "chrome/browser/power_usage_monitor/power_usage_monitor.h"
 #include "chrome/browser/process_singleton.h"
 #include "chrome/browser/ui/startup/startup_browser_creator.h"
 #include "chrome/common/stack_sampling_configuration.h"
 #include "content/public/browser/browser_main_parts.h"
 #include "content/public/common/main_function_params.h"
 
 class BrowserProcessImpl;
 class ChromeBrowserMainExtraParts;
 class FieldTrialSynchronizer;
-class MetricsService;
 class PrefService;
 class ProcessPowerCollector;
 class Profile;
 class StartupBrowserCreator;
 class StartupTimeBomb;
 class ShutdownWatcherHelper;
 class ThreeDAPIObserver;
 class WebUsbDetector;
 
 namespace chrome_browser {
@@ skipping 158 matching lines @@
 
   // Members initialized in PreMainMessageLoopRun, needed in
   // PreMainMessageLoopRunThreadsCreated.
   PrefService* local_state_;
   base::FilePath user_data_dir_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainParts);
 };
 
 #endif  // CHROME_BROWSER_CHROME_BROWSER_MAIN_H_