Re-add the Autofill.SelectedMaskedServerCard metric which was removed in crrev.com/c/1400262.

It shouldn't have been removed, just marked obsolete.

Bug: 0
Change-Id: I0b6bc2eec96b4360621ab07fbed8e721d1cf8b7e
Reviewed-on: https://chromium-review.googlesource.com/c/1489178Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635734}

tools/metrics/ukm/ukm.xml

@@ -553,6 +553,20 @@ be describing additional metrics about the same event.
   </metric>
 </event>
 
+<event name="Autofill.SelectedMaskedServerCard">
+  <obsolete>
+    Deprecated 2/2019
+  </obsolete>
+  <owner>jiahuiguo@google.com</owner>
+  <metric name="MillisecondsSinceFormParsed">
+    <summary>
+      Obsolete.
+
+      Time since form parse.
+    </summary>
+  </metric>
+</event>
+
 <event name="Autofill.SuggestionFilled">
   <owner>jiahuiguo@google.com</owner>
   <summary>