Bind base::PostTaskWithTraits directly

Followup for https://crrev.com/c/1335939

Bug: 795872
Change-Id: I50aef1c108eb2afa09ff18361b77b1110a02df0b
Reviewed-on: https://chromium-review.googlesource.com/c/1356539Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613067}

ios/chrome/browser/browser_state/chrome_browser_state_impl_io_data.mm

@@ -350,12 +350,10 @@ void ChromeBrowserStateImplIOData::ClearNetworkingHistorySinceOnIOThread(
   DCHECK(initialized());
   DCHECK(transport_security_state());
   auto barrier = base::BarrierClosure(
-      2, base::BindOnce(
-             [](base::OnceClosure callback) {
-               base::PostTaskWithTraits(FROM_HERE, {web::WebThread::UI},
-                                        std::move(callback));
-             },
-             completion));
+      2, base::BindOnce(base::IgnoreResult(&base::PostTaskWithTraits),
+                        FROM_HERE, base::TaskTraits(web::WebThread::UI),
+                        std::move(completion)));
+
   transport_security_state()->DeleteAllDynamicDataSince(time, barrier);
   http_server_properties()->Clear(barrier);
 }