[Web Payments] Let subsheets define the initial focus

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

Index: chrome/browser/ui/views/payments/cvc_unmask_view_controller.h
diff --git a/chrome/browser/ui/views/payments/cvc_unmask_view_controller.h b/chrome/browser/ui/views/payments/cvc_unmask_view_controller.h
index b331aaed04c8bf9813561591743208444e71f74d..ab4c62cc5b5449ab3b42f7b2967be088ac50cefa 100644
--- a/chrome/browser/ui/views/payments/cvc_unmask_view_controller.h
+++ b/chrome/browser/ui/views/payments/cvc_unmask_view_controller.h
@@ -85,6 +85,8 @@ class CvcUnmaskViewController
   // active FullCardRequest.
   void CvcConfirmed();
 
+  views::View* GetFirstFocusedView() override;
+
   views::Textfield* cvc_field_;  // owned by the view hierarchy, outlives this.
   autofill::CreditCard credit_card_;
   content::WebContents* web_contents_;