Make MetricsService upload logs through an interface.

components/metrics/metrics_log_uploader.cc

+// Copyright 2014 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/metrics_log_uploader.h"
+
+namespace metrics {
+
+MetricsLogUploader::MetricsLogUploader(
+    const std::string& server_url,
+    const std::string& mime_type,
+    const base::Callback<void(int)>& on_upload_complete)
+    : server_url_(server_url),
+      mime_type_(mime_type),
+      on_upload_complete_(on_upload_complete) {
+}
+
+MetricsLogUploader::~MetricsLogUploader() {
+}
+
+}  // namespace metrics