[Autofill Auth] Updating OptChange request.

This CL ensures that fido_authentication_info is not set if it does not contain
any data.

Bug: 949269
Change-Id: I27ced9ba881d17c66bfc10c8467f9588ff91c091
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863642Reviewed-by: Jared Saul <jsaul@google.com>
Commit-Queue: Manas Verma <manasverma@google.com>
Cr-Commit-Position: refs/heads/master@{#706243}

components/autofill/core/browser/payments/payments_client.cc

@@ -506,12 +506,12 @@ class OptChangeRequest : public PaymentsRequest {
     }
     request_dict.SetKey("reason", base::Value(reason));
 
-    base::Value fido_authentication_info(base::Value::Type::DICTIONARY);
     if (request_details_.fido_authenticator_response.is_dict()) {
+      base::Value fido_authentication_info(base::Value::Type::DICTIONARY);
+
       fido_authentication_info.SetKey(
           "fido_authenticator_response",
           std::move(request_details_.fido_authenticator_response));
-    }
 
       if (!request_details_.card_authorization_token.empty()) {
         fido_authentication_info.SetKey(
@@ -521,6 +521,7 @@ class OptChangeRequest : public PaymentsRequest {
 
       request_dict.SetKey("fido_authentication_info",
                           std::move(fido_authentication_info));
+    }
 
     std::string request_content;
     base::JSONWriter::Write(request_dict, &request_content);