Call Start() from NetMetricsLogUploader.

Before the CL that introduced NetMetricsLogUploader, Start()
was being called from MetricsService::SendStagedLog().

However, it got lost in the refactoring. This re-adds it.

BUG=375771
R=isherman@chromium.org

Review URL: https://codereview.chromium.org/309793006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274306 0039d316-1c4b-4281-b951-d872f2087c98

components/metrics/net/net_metrics_log_uploader.cc

@@ -55,6 +55,7 @@ bool NetMetricsLogUploader::UploadLog(const std::string& log_data,
   // client-side as well.
   current_fetch_->SetLoadFlags(net::LOAD_DO_NOT_SAVE_COOKIES |
                                net::LOAD_DO_NOT_SEND_COOKIES);
+  current_fetch_->Start();
   return true;
 }