[Chromecast] Moves persistent UMA client ID handling to common code.

chromecast/browser/metrics/platform_metrics_providers.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_PLATFORM_METRICS_PROVIDERS_H_
 #define CHROMECAST_BROWSER_METRICS_PLATFORM_METRICS_PROVIDERS_H_
 
-#include "components/metrics/proto/system_profile.pb.h"
-
 namespace metrics {
 class MetricsService;
 }
 
 namespace chromecast {
 
 class CastService;
 
 namespace metrics {
 
 // Build-level hook for different platforms to provide data to MetricsService.
 void RegisterPlatformMetricsProviders(
     ::metrics::MetricsService* metrics_service,
     CastService* cast_servce);
 
-// Returns UMA client ID persisted in the platform.
-const std::string GetPlatformClientID(CastService* cast_servce);
-
-// Called when the UMA client ID has been set.
-void PlatformSetClientID(CastService* cast_servce,
-                         const std::string& client_id);
-
 }  // namespace metrics
 }  // namespace chromecast
 
 #endif  // CHROMECAST_BROWSER_METRICS_PLATFORM_METRICS_PROVIDERS_H_