Fixes formatting of the signed-in setting string on iOS.

ios/chrome/browser/ui/payments/payment_request_view_controller.mm

Index: ios/chrome/browser/ui/payments/payment_request_view_controller.mm
diff --git a/ios/chrome/browser/ui/payments/payment_request_view_controller.mm b/ios/chrome/browser/ui/payments/payment_request_view_controller.mm
index 1c825fbc85621f1c8d1f4f1287296e51554407b1..dd4df01aae7abeb2c07936c9bef2c3d17c031054 100644
--- a/ios/chrome/browser/ui/payments/payment_request_view_controller.mm
+++ b/ios/chrome/browser/ui/payments/payment_request_view_controller.mm
@@ -377,12 +377,10 @@ typedef NS_ENUM(NSInteger, ItemType) {
     footer.text =
         l10n_util::GetNSString(IDS_PAYMENTS_CARD_AND_ADDRESS_SETTINGS);
   } else if ([[_dataSource authenticatedAccountName] length]) {
-    const std::string unformattedString = l10n_util::GetStringUTF8(
-        IDS_PAYMENTS_CARD_AND_ADDRESS_SETTINGS_SIGNED_IN);
-    const std::string accountName =
-        base::SysNSStringToUTF8([_dataSource authenticatedAccountName]);
-    const std::string formattedString =
-        base::StringPrintf(unformattedString.c_str(), accountName.c_str());
+    const base::string16 accountName =
+        base::SysNSStringToUTF16([_dataSource authenticatedAccountName]);

[please use gerrit instead, 2017/05/25 19:42:44]

I would be more comfortable with using std::string here as well (via
base::SysNSStringToUTF8).

[macourteau, 2017/05/25 19:53:47]

There's no variant of GetStringFUTF8 that takes an std::string:
https://cs.chromium.org/chromium/src/ui/base/l10n/l10n_util.h?l=138

+    const std::string formattedString = l10n_util::GetStringFUTF8(
+        IDS_PAYMENTS_CARD_AND_ADDRESS_SETTINGS_SIGNED_IN, accountName);
     footer.text = base::SysUTF8ToNSString(formattedString);
   } else {
     footer.text = l10n_util::GetNSString(