Revert of Move JoinString to the base namespace

chrome/browser/extensions/api/identity/gaia_web_auth_flow.cc

Index: chrome/browser/extensions/api/identity/gaia_web_auth_flow.cc
diff --git a/chrome/browser/extensions/api/identity/gaia_web_auth_flow.cc b/chrome/browser/extensions/api/identity/gaia_web_auth_flow.cc
index d97fca421a354df4ef0c68eb321a3e3e70f60625..6b7232ed00587a25d0e687e6a6a903595793af4a 100644
--- a/chrome/browser/extensions/api/identity/gaia_web_auth_flow.cc
+++ b/chrome/browser/extensions/api/identity/gaia_web_auth_flow.cc
@@ -55,7 +55,7 @@
   std::vector<std::string> client_id_parts;
   base::SplitString(oauth2_client_id, '.', &client_id_parts);
   std::reverse(client_id_parts.begin(), client_id_parts.end());
-  redirect_scheme_ = base::JoinString(client_id_parts, ".");
+  redirect_scheme_ = JoinString(client_id_parts, '.');
   std::string signin_scoped_device_id;
   // profile_ can be nullptr in unittests.
   SigninClient* signin_client =
@@ -69,7 +69,7 @@
   std::string oauth2_authorize_params = base::StringPrintf(
       kOAuth2AuthorizeFormat,
       oauth2_client_id.c_str(),
-      net::EscapeUrlEncodedData(base::JoinString(scopes, " "), true).c_str(),
+      net::EscapeUrlEncodedData(JoinString(scopes, ' '), true).c_str(),
       token_key->extension_id.c_str(),
       redirect_scheme_.c_str(),
       token_key->extension_id.c_str(),