Extend PasswordProtection.DomFeatureExtractionDuration

The code to extract DOM features is undergoing a moderate-size
refactoring and this metric could be useful in diagnosing a regression.

Fixed: 1160884
Change-Id: I9e970610a5b69e2a31d5d4e829cf87b1ec2fccd8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2610956
Auto-Submit: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#840640}

tools/metrics/histograms/histograms_xml/password/histograms.xml

@@ -2320,7 +2320,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="PasswordProtection.DomFeatureExtractionDuration" units="ms"
-    expires_after="2021-01-30">
+    expires_after="2021-07-30">
   <owner>drubery@chromium.org</owner>
   <owner>chrome-safebrowsing-alerts@google.com</owner>
   <summary>