Split the ReportUpdateAttemptMetrics into two functions

Move out the report download metrics into a new function so that
ReportUpdateAttemptMetrics has a reasonable number of parameters.
Create mocks for these two functions also.

Test: unittest pass
Change-Id: Ib9fc33d282a448c7e2d19bb7e7c06619efc2a278
diff --git a/metrics_reporter_android.cc b/metrics_reporter_android.cc
index ebfad0d..4a57918 100644
--- a/metrics_reporter_android.cc
+++ b/metrics_reporter_android.cc
@@ -36,13 +36,8 @@
     base::TimeDelta /* duration */,
     base::TimeDelta /* duration_uptime */,
     int64_t /* payload_size */,
-    int64_t /* payload_bytes_downloaded */,
-    int64_t /* payload_download_speed_bps */,
-    DownloadSource /* download_source */,
     metrics::AttemptResult /* attempt_result */,
-    ErrorCode error_code,
-    metrics::DownloadErrorCode /* payload_download_error_code */,
-    metrics::ConnectionType /* connection_type */) {
+    ErrorCode error_code) {
 // No need to log histogram under sideload mode.
 #ifndef _UE_SIDELOAD
   android::metricslogger::LogHistogram(metrics::kMetricsUpdateEngineErrorCode,