[Payment Request] Refactors edit view controller

ios/chrome/browser/ui/payments/payment_request_edit_view_controller+internal.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 IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_REQUEST_EDIT_VIEW_CONTROLLER_INTERNAL_H_
-#define IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_REQUEST_EDIT_VIEW_CONTROLLER_INTERNAL_H_
-
-#import "ios/chrome/browser/ui/payments/payment_request_edit_view_controller.h"
-#import "ios/chrome/browser/ui/payments/payment_request_edit_view_controller_actions.h"
-
-// Use these as the starting values for section identifier and item type enums
-// in subclasses. These values are chosen to prevent overlapping with the
-// section identifier and item type enums of this class.
-const NSInteger kSectionIdentifierEnumStart = kSectionIdentifierEnumZero + 20;
-const NSInteger kItemTypeEnumStart = kItemTypeEnumZero + 100;
-
-// Internal API for subclasses of PaymentRequestEditViewController.
-@interface PaymentRequestEditViewController (
-    Internal)<PaymentRequestEditViewControllerActions>
-
-// Validates each field. If there is a validation error, displays an error
-// message item in the same section as the field and returns NO. Otherwise
-// removes the error message item in that section if one exists and sets the
-// value on the field. Returns YES if all the fields are validated successfully.
-- (BOOL)validateForm;
-
-// Called after the editor field items have been added to the the collection
-// view model. Subclasses override this method to add items after the editor
-// fields.
-- (void)loadFooterItems;
-
-// Returns the index path for the cell associated with the currently focused
-// text field.
-- (NSIndexPath*)indexPathForCurrentTextField;
-
-@end
-
-#endif  // IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_REQUEST_EDIT_VIEW_CONTROLLER_INTERNAL_H_