chromecast: Cleanup class/struct fwd declarations

chromecast/browser/metrics/cast_stability_metrics_provider.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 CHROMECAST_BROWSER_METRICS_CAST_STABILITY_METRICS_PROVIDER_H_
 #define CHROMECAST_BROWSER_METRICS_CAST_STABILITY_METRICS_PROVIDER_H_
 
 #include "base/macros.h"
 #include "base/process/kill.h"
 #include "components/metrics/metrics_provider.h"
 #include "content/public/browser/browser_child_process_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 class PrefRegistrySimple;
 
 namespace content {
 class RenderProcessHost;
-class WebContents;
 }
 
 namespace metrics {
 class MetricsService;
 }
 
 namespace chromecast {
 namespace metrics {
 
 // CastStabilityMetricsProvider gathers and logs stability-related metrics.
@@ skipping 46 matching lines @@
   // CastStabilityMetricsProvider.
   ::metrics::MetricsService* metrics_service_;
 
   DISALLOW_COPY_AND_ASSIGN(CastStabilityMetricsProvider);
 };
 
 }  // namespace metrics
 }  // namespace chromecast
 
 #endif  // CHROMECAST_BROWSER_METRICS_CAST_STABILITY_METRICS_PROVIDER_H_