Update the incorrect units for two UMA stats.

From the codes, Ash.TouchView.TouchViewActiveTotal and
Ash.TouchView.TouchViewInactiveTotal are both recorded in mins, but they were
not documented correctly in histograms.xml. Thus update them.

Bug: None
Change-Id: I5003e015ff5d9101818501d340494acc6d034e3a
Reviewed-on: https://chromium-review.googlesource.com/c/1423133
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624683}
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 91b1c79..020a3c8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5380,7 +5380,7 @@
   <summary>The proportion of time spent in TouchView during a session.</summary>
 </histogram>
 
-<histogram name="Ash.TouchView.TouchViewActiveTotal" units="seconds">
+<histogram name="Ash.TouchView.TouchViewActiveTotal" units="minutes">
   <owner>girard@chromium.org</owner>
   <summary>The total time that TouchView is active during a session.</summary>
 </histogram>
@@ -5390,7 +5390,7 @@
   <summary>The length of time between TouchView activations.</summary>
 </histogram>
 
-<histogram name="Ash.TouchView.TouchViewInactiveTotal" units="seconds">
+<histogram name="Ash.TouchView.TouchViewInactiveTotal" units="minutes">
   <owner>girard@chromium.org</owner>
   <summary>
     The total time that TouchView is not active during a session.