[ChromeOS] Pass optional email to auth extension.

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index 4e166a818dba0acb6af1330b819bc1d2b13f7154..37b9313f9e9792567e14ed95e4c42597dc6e7b4d 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -273,15 +273,12 @@ void SigninScreenHandler::ShowSigninScreenIfReady() {
     return;
 
   DictionaryValue params;
+  params.SetString("startUrl", kGaiaExtStartPage);
   params.SetString("email", email_);
 
-  std::string url = kGaiaExtStartPage;
   const std::string app_locale = g_browser_process->GetApplicationLocale();
-  if (!app_locale.empty()) {
-    url.append("?hl=");
-    url.append(app_locale);
-  }
-  params.SetString("startUrl", url);
+  if (!app_locale.empty())
+    params.SetString("hl", app_locale);
 
   params.SetBoolean("createAccount",
       UserCrosSettingsProvider::cached_allow_new_user());