Use StringPiece for CreateUploader/NetMetricsLogUploader params.

components/metrics/test_metrics_service_client.cc

Index: components/metrics/test_metrics_service_client.cc
diff --git a/components/metrics/test_metrics_service_client.cc b/components/metrics/test_metrics_service_client.cc
index b68bef847f500fd0fc2d42c66c4bbd1c6c6dc6d2..965cfb1f43aa76c1141d8305d5af878712198302 100644
--- a/components/metrics/test_metrics_service_client.cc
+++ b/components/metrics/test_metrics_service_client.cc
@@ -65,12 +65,11 @@ void TestMetricsServiceClient::CollectFinalMetricsForLog(
 }
 
 std::unique_ptr<MetricsLogUploader> TestMetricsServiceClient::CreateUploader(
-    const std::string& server_url,
-    const std::string& mime_type,
+    base::StringPiece server_url,
+    base::StringPiece mime_type,
     MetricsLogUploader::MetricServiceType service_type,
     const base::Callback<void(int)>& on_upload_complete) {
-  uploader_ = new TestMetricsLogUploader(server_url, mime_type, service_type,
-                                         on_upload_complete);
+  uploader_ = new TestMetricsLogUploader(on_upload_complete);
   return std::unique_ptr<MetricsLogUploader>(uploader_);
 }