chrome: Cleanup class/struct forward declarations

chrome/browser/metrics/chrome_metrics_service_accessor.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_ACCESSOR_H_
 #define CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 
 #include <stdint.h>
 #include <string>
 #include <vector>
@@ skipping 17 matching lines @@
 class ArcOptInPreferenceHandler;
 }
 
 namespace chrome {
 void AttemptRestart();
 namespace android {
 class ExternalDataUseObserverBridge;
 }
 }
 
-namespace component_updater {
-class ComponentUpdateService;
-}
-
 namespace domain_reliability {
 class DomainReliabilityServiceFactory;
 }
 
 namespace extensions {
 class ChromeExtensionWebContentsObserver;
 class ChromeMetricsPrivateDelegate;
 class FileManagerPrivateIsUMAEnabledFunction;
 }
 
@@ skipping 101 matching lines @@
   // with g_browser_process->metrics_service(). See that function's declaration
   // for details.
   static bool RegisterSyntheticFieldTrialWithNameHash(
       uint32_t trial_name_hash,
       const std::string& group_name);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ChromeMetricsServiceAccessor);
 };
 
 #endif  // CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_