Use StringPiece for CreateUploader/NetMetricsLogUploader params.

components/metrics/test_metrics_log_uploader.cc

 // Copyright 2017 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.
 
 #include "components/metrics/test_metrics_log_uploader.h"
 #include "components/metrics/metrics_log_uploader.h"
 
 namespace metrics {
 
 TestMetricsLogUploader::TestMetricsLogUploader(
-    const std::string& server_url,
-    const std::string& mime_type,
-    MetricsLogUploader::MetricServiceType service_type,
     const base::Callback<void(int)>& on_upload_complete)
-    : MetricsLogUploader(server_url,
-                         mime_type,
-                         service_type,
-                         on_upload_complete),
-      is_uploading_(false) {}
+    : on_upload_complete_(on_upload_complete), is_uploading_(false) {}
 
 TestMetricsLogUploader::~TestMetricsLogUploader() = default;
 
 void TestMetricsLogUploader::CompleteUpload(int response_code) {
   DCHECK(is_uploading_);
   is_uploading_ = false;
   on_upload_complete_.Run(response_code);
 }
 
 void TestMetricsLogUploader::UploadLog(const std::string& compressed_log_data,
                                        const std::string& log_hash) {
   DCHECK(!is_uploading_);
   is_uploading_ = true;
 }
 
 }  // namespace metrics