Revert "Monorail: Make comment numbers on the FLT page based on displayed sections."

This reverts commit d1d54387560870f290474017fd24807f4667b4bc.

Reason for revert: Implementing this in only the frontend means notification emails will have different numbers than the listed comments. 

Original change's description:
> Monorail: Make comment numbers on the FLT page based on displayed sections.
> 
> Bug: monorail:4582
> Change-Id: I280338dcd6afb58a57c1c70792727e71bba0e36b
> Reviewed-on: https://chromium-review.googlesource.com/c/1403888
> Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#19906}

TBR=zhangtiff@chromium.org,ehmaldonado@chromium.org,jojwang@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: monorail:4582
Change-Id: I430eaed5ac157f341a54d03d151bcea50a764b8f
Reviewed-on: https://chromium-review.googlesource.com/c/1410202
Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Jason Robbins <jrobbins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#19970}
Cr-Mirrored-Commit: 1d85460b28207034bb7b06e5a6855254ab65ec44
diff --git a/appengine/monorail/elements/flt/mr-comments/mr-comments.html b/appengine/monorail/elements/flt/mr-comments/mr-comments.html
index 74e0a23..1290406 100644
--- a/appengine/monorail/elements/flt/mr-comments/mr-comments.html
+++ b/appengine/monorail/elements/flt/mr-comments/mr-comments.html
@@ -69,13 +69,7 @@
     <template is="dom-repeat" items="[[comments]]" as="comment">
       <div class="card-comment" hidden$=[[_computeCommentHidden(_commentsHidden,_commentsHiddenCount,index)]]>
         <span role="heading" aria-level$="[[headingLevel]]" class="comment-header">
-          <!-- We use indices rather than sequenceNums for comments because
-            sequenceNums are global across all comments on the page. This
-            is confusing to users because a page can have multiple lists
-            of comments (ie: within approvals and the main comment list),
-            so using unique sequenceNums causes comments to appear to
-            "skip" numbers when listed out in one section. -->
-          Comment [[_addOne(index)]] by
+          Comment [[comment.sequenceNum]] by
           <mr-user-link display-name="[[comment.commenter.displayName]]" user-id="[[comment.commenter.userId]]"></mr-user-link> on
           <chops-timestamp timestamp="[[comment.timestamp]]"></chops-timestamp>
           <template is="dom-if" if=[[_offerCommentOptions(comment)]]>
diff --git a/appengine/monorail/elements/flt/mr-comments/mr-comments.js b/appengine/monorail/elements/flt/mr-comments/mr-comments.js
index ca8859a..1be42d0 100644
--- a/appengine/monorail/elements/flt/mr-comments/mr-comments.js
+++ b/appengine/monorail/elements/flt/mr-comments/mr-comments.js
@@ -152,10 +152,6 @@
     return commentsHidden ? 'Show' : 'Hide';
   }
 
-  _addOne(count) {
-    return count + 1;
-  }
-
   _pluralize(count, baseWord, pluralWord) {
     pluralWord = pluralWord || `${baseWord}s`;
     return count == 1 ? baseWord : pluralWord;