Use StringPiece for CreateUploader/NetMetricsLogUploader params.

chromecast/browser/metrics/cast_metrics_service_client.h

Index: chromecast/browser/metrics/cast_metrics_service_client.h
diff --git a/chromecast/browser/metrics/cast_metrics_service_client.h b/chromecast/browser/metrics/cast_metrics_service_client.h
index a45cee9c58b2e8fd05b3158234c8a25748cb4b58..655448015d576b468e6c92d50e7ee6ad1cd2cf77 100644
--- a/chromecast/browser/metrics/cast_metrics_service_client.h
+++ b/chromecast/browser/metrics/cast_metrics_service_client.h
@@ -80,8 +80,8 @@ class CastMetricsServiceClient : public ::metrics::MetricsServiceClient,
   void CollectFinalMetricsForLog(const base::Closure& done_callback) override;
   std::string GetMetricsServerUrl() override;
   std::unique_ptr<::metrics::MetricsLogUploader> CreateUploader(
-      const std::string& server_url,
-      const std::string& mime_type,
+      const base::StringPiece& server_url,
+      const base::StringPiece& mime_type,
       ::metrics::MetricsLogUploader::MetricServiceType service_type,
       const base::Callback<void(int)>& on_upload_complete) override;
   base::TimeDelta GetStandardUploadInterval() override;