Use constexpr TaskTraits constructor in ios.

ios/web/net/crw_cert_verification_controller.mm

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/net/crw_cert_verification_controller.h"
 
 #include <memory>
 
 #import "base/ios/block_types.h"
 #include "base/logging.h"
@@ skipping 176 matching lines @@
       }));
 }
 
 - (void)verifyTrust:(base::ScopedCFTypeRef<SecTrustRef>)trust
     completionHandler:(void (^)(SecTrustResultType))completionHandler {
   DCHECK_CURRENTLY_ON(web::WebThread::UI);
   DCHECK(completionHandler);
   // SecTrustEvaluate performs trust evaluation synchronously, possibly making
   // network requests. The UI thread should not be blocked by that operation.
   base::PostTaskWithTraits(
-      FROM_HERE,
-      base::TaskTraits().WithShutdownBehavior(
-          base::TaskShutdownBehavior::BLOCK_SHUTDOWN),
+      FROM_HERE, {base::TaskShutdownBehavior::BLOCK_SHUTDOWN},
       base::BindBlockArc(^{
         SecTrustResultType trustResult = kSecTrustResultInvalid;
         if (SecTrustEvaluate(trust.get(), &trustResult) != errSecSuccess) {
           trustResult = kSecTrustResultInvalid;
         }
         // Use GCD API, which is guaranteed to be called during shutdown.
         dispatch_async(dispatch_get_main_queue(), ^{
           completionHandler(trustResult);
         });
       }));
@@ skipping 24 matching lines @@
 
   web::CertPolicy::Judgment judgment = _certPolicyCache->QueryPolicy(
       leafCert.get(), base::SysNSStringToUTF8(host), certStatus);
 
   return (judgment == web::CertPolicy::ALLOWED)
              ? web::CERT_ACCEPT_POLICY_RECOVERABLE_ERROR_ACCEPTED_BY_USER
              : web::CERT_ACCEPT_POLICY_RECOVERABLE_ERROR_UNDECIDED_BY_USER;
 }
 
 @end