[Payment Request] Refactors the edit view controller

ios/chrome/browser/ui/payments/payment_request_edit_view_controller_data_source.h

Index: ios/chrome/browser/ui/payments/payment_request_edit_view_controller_data_source.h
diff --git a/ios/chrome/browser/ui/payments/payment_request_edit_view_controller_data_source.h b/ios/chrome/browser/ui/payments/payment_request_edit_view_controller_data_source.h
index 009128b0294db3ef34e3d60458b362d4f4ca88c9..e56f1e22e518adf9e8541cd839253bfec18f8083 100644
--- a/ios/chrome/browser/ui/payments/payment_request_edit_view_controller_data_source.h
+++ b/ios/chrome/browser/ui/payments/payment_request_edit_view_controller_data_source.h
@@ -8,10 +8,28 @@
 #import <Foundation/Foundation.h>
 
 @class EditorField;
+@class CollectionViewItem;
+
+// The possible states the view controller can be in.
+typedef NS_ENUM(NSInteger, EditViewControllerState) {
+  // The view controller is used for creating.
+  EditViewControllerStateCreate,
+  // The view controller is used to editing.
+  EditViewControllerStateEdit,
+};
 
 // Data source protocol for PaymentRequestEditViewController.
 @protocol PaymentRequestEditViewControllerDataSource<NSObject>
 
+// The current state of the view controller.
+@property(nonatomic, assign) EditViewControllerState state;
+
+// Returns the header item. May be nil.
+- (CollectionViewItem*)headerItem;
+
+// Returns whether the header item should hide its background.
+- (BOOL)shouldHideBackgroundForHeaderItem;
+
 // Returns the list of field definitions for the editor.
 - (NSArray<EditorField*>*)editorFields;