Fix time units in plotted charts

Bug: webrtc:10138
Change-Id: I057caa8fadb41ff09733b2bf435cee2a1f2c70c7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/152822
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29183}
diff --git a/rtc_tools/metrics_plotter.py b/rtc_tools/metrics_plotter.py
index d045763..54ccee9 100644
--- a/rtc_tools/metrics_plotter.py
+++ b/rtc_tools/metrics_plotter.py
@@ -62,7 +62,7 @@
       y_values.append(sample['value'])
 
     plt.ylabel('%s (%s)' % (metric[GRAPH_NAME], metric[UNITS]))
-    plt.xlabel('time (ms)')
+    plt.xlabel('time (s)')
     plt.title(metric[GRAPH_NAME])
     plt.plot(x_values, y_values)