opt in web share to ukm use counter

Change-Id: I9806545fd84b6e17d1d3c4c81155d099396d89cd
Reviewed-on: https://chromium-review.googlesource.com/c/1352587Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Luna Lu <loonybear@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612743}

chrome/browser/page_load_metrics/observers/use_counter/ukm_features.cc

@@ -75,6 +75,7 @@ bool IsAllowedUkmFeature(blink::mojom::WebFeature feature) {
           WebFeature::kUpdateWithoutShippingOptionOnShippingOptionChange,
           WebFeature::kSignedExchangeInnerResponseInMainFrame,
           WebFeature::kSignedExchangeInnerResponseInSubFrame,
+          WebFeature::kWebShareShare,
       }));
   return opt_in_features->count(feature);
 }