[bookmarks] Adopt various patterned histograms

This rewrites histograms.xml to avoid text duplication.

Change-Id: I80ae3d3b7e6873c1d193ef4520d63fc3c6163982
Bug: None
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2517594
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Weilun Shi <sweilun@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836566}

tools/metrics/histograms/histograms_xml/others/histograms.xml

@@ -1536,75 +1536,38 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
-<histogram name="Bookmarks.Count.OnProfileLoad.DuplicateUrl2" units="bookmarks"
-    expires_after="2021-06-06">
-  <owner>mastiz@chromium.org</owner>
-  <owner>sky@chromium.org</owner>
-  <summary>
-    The number of bookmarks a user has saved with a URL that is also present in
-    at least one other bookmark. This excludes not only folders (which don't
-    have a URL) but it also excludes one bookmark per unique URL (that is, all
-    except one are considered duplicates). Recorded when bookmarks are loaded
-    into storage from disk if there is at least one duplicate.
-  </summary>
-</histogram>
-
-<histogram name="Bookmarks.Count.OnProfileLoad.DuplicateUrlAndTitle"
+<histogram name="Bookmarks.Count.OnProfileLoad.Duplicate{UniquenessCriterion}"
     units="bookmarks" expires_after="2021-06-06">
   <owner>mastiz@chromium.org</owner>
   <owner>sky@chromium.org</owner>
   <summary>
-    The number of bookmarks a user has saved with a URL and title pair that is
-    also present in at least one other bookmark. This excludes not only folders
-    (which don't have a URL) but it also excludes one bookmark per unique URL
-    and title pair (that is, all except one are considered duplicates). Recorded
-    when bookmarks are loaded into storage from disk if there is at least one
-    duplicate.
-  </summary>
-</histogram>
-
-<histogram name="Bookmarks.Count.OnProfileLoad.DuplicateUrlAndTitleAndParent"
-    units="bookmarks" expires_after="2021-04-04">
-  <owner>mastiz@chromium.org</owner>
-  <owner>sky@chromium.org</owner>
-  <summary>
-    The number of bookmarks a user has saved with a URL, title and parent triple
-    that is also present in at least one other bookmark. This excludes not only
+    The number of bookmarks a user has saved with a {UniquenessCriterion} that
+    is also present in at least one other bookmark. This excludes not only
     folders (which don't have a URL) but it also excludes one bookmark per
-    unique URL, title and parent triple (that is, all except one are considered
+    unique {UniquenessCriterion} (that is, all except one are considered
     duplicates). Recorded when bookmarks are loaded into storage from disk if
     there is at least one duplicate.
   </summary>
+  <token key="UniquenessCriterion">
+    <variant name="Url2" summary="URL"/>
+    <variant name="UrlAndTitle" summary="URL-title pair"/>
+    <variant name="UrlAndTitleAndParent" summary="URL-title-parent triple"/>
+  </token>
 </histogram>
 
-<histogram name="Bookmarks.Count.OnProfileLoad.UniqueUrl" units="bookmarks"
-    expires_after="2021-06-06">
-  <owner>mastiz@chromium.org</owner>
-  <owner>sky@chromium.org</owner>
-  <summary>
-    The number of unique URLs among bookmarks saved by the user. Recorded when
-    bookmarks are loaded into storage from disk.
-  </summary>
-</histogram>
-
-<histogram name="Bookmarks.Count.OnProfileLoad.UniqueUrlAndTitle"
-    units="bookmarks" expires_after="2021-06-06">
-  <owner>mastiz@chromium.org</owner>
-  <owner>sky@chromium.org</owner>
-  <summary>
-    The number of unique URL-title pairs among bookmarks saved by the user.
-    Recorded when bookmarks are loaded into storage from disk.
-  </summary>
-</histogram>
-
-<histogram name="Bookmarks.Count.OnProfileLoad.UniqueUrlAndTitleAndParent"
+<histogram name="Bookmarks.Count.OnProfileLoad.Unique{UniquenessCriterion}"
     units="bookmarks" expires_after="2021-06-06">
   <owner>mastiz@chromium.org</owner>
   <owner>sky@chromium.org</owner>
   <summary>
-    The number of unique URL-title-parent triples among bookmarks saved by the
+    The number of unique {UniquenessCriterion}s among bookmarks saved by the
     user. Recorded when bookmarks are loaded into storage from disk.
   </summary>
+  <token key="UniquenessCriterion">
+    <variant name="Url" summary="URL"/>
+    <variant name="UrlAndTitle" summary="URL-title pair"/>
+    <variant name="UrlAndTitleAndParent" summary="URL-title-parent triple"/>
+  </token>
 </histogram>
 
 <histogram name="Bookmarks.Count.OpenInIncognito" units="bookmarks"