Use StringPiece for CreateUploader/NetMetricsLogUploader params.

chromecast/browser/metrics/cast_metrics_service_client.cc

Index: chromecast/browser/metrics/cast_metrics_service_client.cc
diff --git a/chromecast/browser/metrics/cast_metrics_service_client.cc b/chromecast/browser/metrics/cast_metrics_service_client.cc
index 0d61688a36f3e3cc2bfba28baba5562a807ebf54..eee2b0106814ff86d0ad40cec6edbc00745887d4 100644
--- a/chromecast/browser/metrics/cast_metrics_service_client.cc
+++ b/chromecast/browser/metrics/cast_metrics_service_client.cc
@@ -243,8 +243,8 @@ std::string CastMetricsServiceClient::GetMetricsServerUrl() {
 
 std::unique_ptr<::metrics::MetricsLogUploader>
 CastMetricsServiceClient::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) {
   return std::unique_ptr<::metrics::MetricsLogUploader>(