Extend expiry date of Offline histogram

These histograms are still needed as the experiment analysis is
still ongoing.

Bug: 1151983
Change-Id: Ib0a5884c8b8ec0adbc1623454da2fb60af518571
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2564444
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832422}

tools/metrics/histograms/histograms_xml/offline/OWNERS

+# If these reviewers are unavailable, please send CLs to
+# <chromium-metrics-reviews@google.com>. See tools/metrics/histograms/histograms_xml/OWNERS
+# for details.
+tbansal@chromium.org
\ No newline at end of file

tools/metrics/histograms/histograms_xml/offline/histograms.xml

@@ -23,6 +23,8 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="OfflineIndicator.ConnectivityChanged.DeviceState.Offline"
     enum="OfflineIndicatorSurfaceState" expires_after="2021-05-09">
+  <owner>curranmax@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
   <owner>sinansahin@google.com</owner>
   <owner>twellington@chromium.org</owner>
   <summary>
@@ -33,7 +35,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="OfflineIndicator.ConnectivityChanged.DeviceState.Online"
-    enum="OfflineIndicatorSurfaceState" expires_after="2021-01-01">
+    enum="OfflineIndicatorSurfaceState" expires_after="2021-05-09">
+  <owner>curranmax@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
   <owner>sinansahin@google.com</owner>
   <owner>twellington@chromium.org</owner>
   <summary>
@@ -55,6 +59,8 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="OfflineIndicator.ShownDuration" units="s"
     expires_after="2021-05-09">
+  <owner>curranmax@chromium.org</owner>
+  <owner>tbansal@chromium.org</owner>
   <owner>sinansahin@google.com</owner>
   <owner>twellington@chromium.org</owner>
   <summary>