metrics: use TimeDelta for upload_interval

Use TimeDelta instead of int interpreted as seconds.

BUG=None
TEST=Unittests.

Change-Id: I18db8d558303291ab86b26c68c89203e0364b623
Reviewed-on: https://chromium-review.googlesource.com/222611
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
diff --git a/metrics/metrics_daemon.h b/metrics/metrics_daemon.h
index 7c7f8d2..f4f1430 100644
--- a/metrics/metrics_daemon.h
+++ b/metrics/metrics_daemon.h
@@ -37,7 +37,7 @@
             const std::string& vmstats_path,
             const std::string& cpuinfo_max_freq_path,
             const std::string& scaling_max_freq_path,
-            int upload_interval_secs,
+            const base::TimeDelta& upload_interval,
             const std::string& server,
             const std::string& metrics_file,
             const std::string& config_root);
@@ -379,7 +379,7 @@
   std::string scaling_max_freq_path_;
   std::string cpuinfo_max_freq_path_;
 
-  int upload_interval_secs_;
+  base::TimeDelta upload_interval_;
   std::string server_;
   std::string metrics_file_;