Add Login.UsersActiveDaily and Login.UsersActive28Days metrics.

Implementation: http://crrev.com/c/chromiumos/platform2/+/2073263

Bug: 1052268
Change-Id: I4fb10b2868f4d4296837c23f0da632857711a285
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2072855
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744916}

tools/metrics/histograms/histograms.xml

@@ -67941,6 +67941,26 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Login.UsersActive28Days" units="users"
+    expires_after="2021-02-28">
+  <owner>alemate@chromium.org</owner>
+  <owner>achuith@chromium.org</owner>
+  <summary>
+    Chrome OS histogram that keeps track of number of users who have logged in
+    in the last 28 days. Reported on every boot and once a day after that.
+  </summary>
+</histogram>
+
+<histogram name="Login.UsersActiveDaily" units="users"
+    expires_after="2021-02-28">
+  <owner>alemate@chromium.org</owner>
+  <owner>achuith@chromium.org</owner>
+  <summary>
+    Chrome OS histogram that keeps track of number of users who have logged in
+    in the last day. Reported on every boot and once a day after that.
+  </summary>
+</histogram>
+
 <histogram name="Login.UsersActiveWeekly" units="users"
     expires_after="2020-12-01">
   <owner>alemate@chromium.org</owner>