histograms.xml: add Network.Shill.CumulativeTimeOnLine.*

Implementation CL:
https://chromium-review.googlesource.com/c/aosp/platform/system/connectivity/shill/+/1220430

BUG=chromium:729335
TEST=none

Change-Id: I00fe89328d9ec0f910b354733fb1914838c5d75c
Reviewed-on: https://chromium-review.googlesource.com/1234696
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Robert Kaplow (sloooow) <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593579}

tools/metrics/histograms/histograms.xml

@@ -60389,6 +60389,19 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Network.Shill.CumulativeTimeOnline" units="seconds">
+  <owner>kirtika@chromium.org</owner>
+  <owner>semenzato@chromium.org</owner>
+  <summary>
+    Chrome OS device time on line in the previous 24-hour sample period.
+    &quot;On line&quot; means shill believes the device is on the internet. The
+    shill state is sampled every 5 minutes. The start of each 24-hour period is
+    the end of the previous period, unless the device is inactive at that time
+    (suspended or off), in which case it is the time of the next
+    resume/power-on.
+  </summary>
+</histogram>
+
 <histogram name="Network.Shill.DarkResumeActionResult"
     enum="ShillSuspendTerminationDarkResumeActionResult">
   <owner>benchan@chromium.org</owner>
@@ -131108,6 +131121,13 @@ uploading your change for review.
   <affected-histogram name="Setup.Install.UnpackFullArchiveTime"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="ShillCumulativeTimeOnline" separator=".">
+  <suffix name="Any" label="Any connection type"/>
+  <suffix name="Cellular" label="Cellular connection"/>
+  <suffix name="Wifi" label="WiFi connection"/>
+  <affected-histogram name="Network.Shill.CumulativeTimeOnline"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="ShillWiFiRememberedNetworkSecurityMode" separator=".">
   <suffix name="802_1x" label="Network is secured with 802.1x"/>
   <suffix name="none" label="Network is not secured"/>