Revert of Move JoinString to the base namespace

extensions/common/api/sockets/sockets_manifest_permission.cc

Index: extensions/common/api/sockets/sockets_manifest_permission.cc
diff --git a/extensions/common/api/sockets/sockets_manifest_permission.cc b/extensions/common/api/sockets/sockets_manifest_permission.cc
index 6dbd4fc311c29cb8f073b8b31f9ef7561689bece..0f7613e0d13836b068dc52bc0031df7522dc8cb5 100644
--- a/extensions/common/api/sockets/sockets_manifest_permission.cc
+++ b/extensions/common/api/sockets/sockets_manifest_permission.cc
@@ -131,9 +131,9 @@
       messages->push_back(PermissionMessage(
           PermissionMessage::kSocketDomainHosts,
           l10n_util::GetStringFUTF16(
-              id, base::JoinString(std::vector<base::string16>(domains.begin(),
-                                                               domains.end()),
-                                   base::ASCIIToUTF16(" ")))));
+              id, JoinString(std::vector<base::string16>(domains.begin(),
+                                                         domains.end()),
+                             ' '))));
     }
     if (ids) {
       for (const auto& domain : domains)
@@ -163,9 +163,9 @@
       messages->push_back(PermissionMessage(
           PermissionMessage::kSocketSpecificHosts,
           l10n_util::GetStringFUTF16(
-              id, base::JoinString(std::vector<base::string16>(
-                                       hostnames.begin(), hostnames.end()),
-                                   base::ASCIIToUTF16(" ")))));
+              id, JoinString(std::vector<base::string16>(hostnames.begin(),
+                                                         hostnames.end()),
+                             ' '))));
     }
     if (ids) {
       for (const auto& hostname : hostnames)