[ios] Stop recording forward items counting histograms

Bug: 1140063
Change-Id: I75ed31301df82036f1f9d6b59f642c54d3d38071
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2506557Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822194}

ios/web/navigation/crw_wk_navigation_handler.mm

@@ -1052,14 +1052,6 @@ void ReportOutOfSyncURLInDidStartProvisionalNavigation(
     didFinishNavigation:(WKNavigation*)navigation {
   [self didReceiveWKNavigationDelegateCallback];
 
-  NSUInteger forwardItemCount = webView.backForwardList.forwardList.count;
-  base::UmaHistogramBoolean("Session.WebStates.HasForwardItemsAfterNavigation",
-                            forwardItemCount > 0);
-  if (forwardItemCount > 0) {
-    base::UmaHistogramCounts100(
-        "Session.WebStates.ForwardItemsCountAfterNavigation", forwardItemCount);
-  }
-
   // Sometimes |webView:didFinishNavigation| arrives before
   // |webView:didCommitNavigation|. Explicitly trigger post-commit processing.
   bool navigationCommitted =

tools/metrics/histograms/histograms_xml/session/histograms.xml

@@ -421,6 +421,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="Session.WebStates.ForwardItemsCountAfterNavigation"
     units="items" expires_after="2020-12-01">
+  <obsolete>
+    Removed 10/2020.
+  </obsolete>
   <owner>ajuma@chromium.org</owner>
   <owner>eugenebut@chromium.org</owner>
   <owner>gambard@chromium.org</owner>
@@ -435,6 +438,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="Session.WebStates.HasForwardItemsAfterNavigation"
     enum="BooleanPresent" expires_after="2020-12-01">
+  <obsolete>
+    Removed 10/2020.
+  </obsolete>
   <owner>ajuma@chromium.org</owner>
   <owner>eugenebut@chromium.org</owner>
   <owner>gambard@chromium.org</owner>