Revert of Move JoinString to the base namespace

extensions/browser/api/vpn_provider/vpn_provider_api.cc

Index: extensions/browser/api/vpn_provider/vpn_provider_api.cc
diff --git a/extensions/browser/api/vpn_provider/vpn_provider_api.cc b/extensions/browser/api/vpn_provider/vpn_provider_api.cc
index e3b80aed2e0b54054b8538e8aa2880c2ec1f7f86..069f171fb7e7272e8d76a7f4877971ec9c30f8ef 100644
--- a/extensions/browser/api/vpn_provider/vpn_provider_api.cc
+++ b/extensions/browser/api/vpn_provider/vpn_provider_api.cc
@@ -112,14 +112,13 @@
   parameter_value->SetStringWithoutPathExpansion(
       shill::kSubnetPrefixParameterThirdPartyVpn, cidr_parts[1]);
 
-  std::string ip_delimiter(1, shill::kIPDelimiter);
   parameter_value->SetStringWithoutPathExpansion(
       shill::kExclusionListParameterThirdPartyVpn,
-      base::JoinString(parameters.exclusion_list, ip_delimiter));
+      JoinString(parameters.exclusion_list, shill::kIPDelimiter));
 
   parameter_value->SetStringWithoutPathExpansion(
       shill::kInclusionListParameterThirdPartyVpn,
-      base::JoinString(parameters.inclusion_list, ip_delimiter));
+      JoinString(parameters.inclusion_list, shill::kIPDelimiter));
 
   if (parameters.mtu) {
     parameter_value->SetStringWithoutPathExpansion(
@@ -132,16 +131,15 @@
         *parameters.broadcast_address);
   }
 
-  std::string non_ip_delimiter(1, shill::kNonIPDelimiter);
   if (parameters.domain_search) {
     parameter_value->SetStringWithoutPathExpansion(
         shill::kDomainSearchParameterThirdPartyVpn,
-        base::JoinString(*parameters.domain_search, non_ip_delimiter));
+        JoinString(*parameters.domain_search, shill::kNonIPDelimiter));
   }
 
   parameter_value->SetStringWithoutPathExpansion(
       shill::kDnsServersParameterThirdPartyVpn,
-      base::JoinString(parameters.dns_servers, ip_delimiter));
+      JoinString(parameters.dns_servers, shill::kIPDelimiter));
 
   return;
 }