Move string helper functions to components/core for iOS use.

components/payments/core/strings_util.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_PAYMENTS_CORE_STRINGS_UTIL_H_
+#define COMPONENTS_PAYMENTS_CORE_STRINGS_UTIL_H_
+
+#include "base/strings/string16.h"
+#include "components/payments/core/payment_options_provider.h"
+
+namespace payments {
+
+// Gets the appropriate display string for the Shipping Address string for the
+// given PaymentShippingType.
+base::string16 GetShippingAddressSectionString(
+    PaymentShippingType shipping_type);
+
+// Gets the appropriate display string for the Shipping Option string for the
+// given PaymentShippingType.
+base::string16 GetShippingOptionSectionString(
+    PaymentShippingType shipping_type);
+
+}  // namespace payments
+
+#endif  // COMPONENTS_PAYMENTS_CORE_STRINGS_UTIL_H_