Extend the expiry of some on-demand update check histograms.

These GoogleUpdate. metrics will be useful through 2021 while Omaha 4 is
being deployed.

BUG=1138415
R=waffles@chromium.org

Change-Id: Ife9baf6a1d3391741bc5b4f2ce944aace56019a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2484442
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Auto-Submit: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818453}

tools/metrics/histograms/histograms_xml/google/histograms.xml

@@ -21,7 +21,8 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histograms>
 
-<histogram name="GoogleUpdate.ErrorHresult" enum="Hresult" expires_after="M86">
+<histogram name="GoogleUpdate.ErrorHresult" enum="Hresult"
+    expires_after="2021-12-31">
   <owner>grt@chromium.org</owner>
   <owner>ydago@chromium.org</owner>
   <summary>The HRESULT for a failed on-demand update check.</summary>
@@ -212,14 +213,14 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="GoogleUpdate.UpdateErrorCode" enum="GoogleUpdateErrorCode"
-    expires_after="M86">
+    expires_after="2021-12-31">
   <owner>grt@chromium.org</owner>
   <owner>ydago@chromium.org</owner>
   <summary>The error code for a failed on-demand update check.</summary>
 </histogram>
 
 <histogram name="GoogleUpdate.UpgradeResult" enum="GoogleUpdateUpgradeStatus"
-    expires_after="M86">
+    expires_after="2021-12-31">
   <owner>grt@chromium.org</owner>
   <owner>ydago@chromium.org</owner>
   <summary>The result of an on-demand update check.</summary>