Remove dependence on a message loop for net::PathBuilder.

components/cast_certificate/cast_cert_validator.cc

Index: components/cast_certificate/cast_cert_validator.cc
diff --git a/components/cast_certificate/cast_cert_validator.cc b/components/cast_certificate/cast_cert_validator.cc
index bcd0a86288781ac14428c2858218050a98dd4a12..2a48ca3e9317578112e4f1edfba8276272a0f505 100644
--- a/components/cast_certificate/cast_cert_validator.cc
+++ b/components/cast_certificate/cast_cert_validator.cc
@@ -310,8 +310,7 @@ bool VerifyDeviceCertUsingCustomTrustStore(
                                     signature_policy.get(), verification_time,
                                     &result);
   path_builder.AddCertIssuerSource(&intermediate_cert_issuer_source);
-  net::CompletionStatus rv = path_builder.Run(base::Closure());
-  DCHECK_EQ(rv, net::CompletionStatus::SYNC);
+  path_builder.Run();
   if (!result.HasValidPath()) {
     // TODO(crbug.com/634443): Log error information.
     return false;