[Web Payments] Let subsheets define the initial focus

chrome/browser/ui/views/payments/cvc_unmask_view_controller.cc

 // 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.
 
 #include "chrome/browser/ui/views/payments/cvc_unmask_view_controller.h"
 
 #include <memory>
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/autofill/risk_util.h"
@@ skipping 193 matching lines @@
   }
 
   dialog()->ShowProcessingSpinner();
 }
 
 bool CvcUnmaskViewController::GetSheetId(DialogViewID* sheet_id) {
   *sheet_id = DialogViewID::CVC_UNMASK_SHEET;
   return true;
 }
 
+views::View* CvcUnmaskViewController::GetFirstFocusedView() {
+  return cvc_field_;
+}
+
 }  // namespace payments