Use StringPiece for CreateUploader/NetMetricsLogUploader params.

android_webview/native/aw_metrics_service_client_impl.h

 // 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.
 
 #ifndef ANDROID_WEBVIEW_NATIVE_AW_METRICS_SERVICE_CLIENT_IMPL_
 #define ANDROID_WEBVIEW_NATIVE_AW_METRICS_SERVICE_CLIENT_IMPL_
 
 #include "android_webview/browser/aw_metrics_service_client.h"
 
 #include <jni.h>
@@ skipping 36 matching lines @@
   void SetMetricsClientId(const std::string& client_id) override;
   int32_t GetProduct() override;
   std::string GetApplicationLocale() override;
   bool GetBrand(std::string* brand_code) override;
   metrics::SystemProfileProto::Channel GetChannel() override;
   std::string GetVersionString() override;
   void InitializeSystemProfileMetrics(
       const base::Closure& done_callback) override;
   void CollectFinalMetricsForLog(const base::Closure& done_callback) override;
   std::unique_ptr<metrics::MetricsLogUploader> CreateUploader(
-      const std::string& server_url,
-      const std::string& mime_type,
+      base::StringPiece server_url,
+      base::StringPiece mime_type,
       metrics::MetricsLogUploader::MetricServiceType service_type,
       const base::Callback<void(int)>& on_upload_complete) override;
   base::TimeDelta GetStandardUploadInterval() override;
 
  private:
   AwMetricsServiceClientImpl();
   ~AwMetricsServiceClientImpl() override;
 
   void InitializeWithGUID(std::string* guid);
 
   bool is_enabled_;
   PrefService* pref_service_;
   net::URLRequestContextGetter* request_context_;
   std::unique_ptr<metrics::MetricsStateManager> metrics_state_manager_;
   std::unique_ptr<metrics::MetricsService> metrics_service_;
 
   DISALLOW_COPY_AND_ASSIGN(AwMetricsServiceClientImpl);
 };
 
 bool RegisterAwMetricsServiceClient(JNIEnv* env);
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_NATIVE_AW_METRICS_SERVICE_CLIENT_IMPL_