[Payments] Add support for required fields in editor validation

chrome/browser/ui/views/payments/editor_view_controller.h

Index: chrome/browser/ui/views/payments/editor_view_controller.h
diff --git a/chrome/browser/ui/views/payments/editor_view_controller.h b/chrome/browser/ui/views/payments/editor_view_controller.h
index 14a521aef415a60f42c6b2d8ac79c84baac6cb5b..512fb272d0c51c9cae72770d68917a8723957e25 100644
--- a/chrome/browser/ui/views/payments/editor_view_controller.h
+++ b/chrome/browser/ui/views/payments/editor_view_controller.h
@@ -34,12 +34,21 @@ struct EditorField {
 
   EditorField(autofill::ServerFieldType type,
               const base::string16& label,
-              LengthHint length_hint)
-      : type(type), label(label), length_hint(length_hint) {}
-
+              LengthHint length_hint,
+              bool required)
+      : type(type),
+        label(label),
+        length_hint(length_hint),
+        required(required) {}
+
+  // Data type in the field.
   const autofill::ServerFieldType type;
+  // Label to be shown alongside the field.
   const base::string16 label;
+  // Hint about the length of this field's contents.
   LengthHint length_hint;
+  // Whether the field is required.
+  bool required;
 };
 
 // The PaymentRequestSheetController subtype for the editor screens of the