PaymentHandler: Implement PaymentInstruments.keys().

content/browser/payments/payment_manager.h

Index: content/browser/payments/payment_manager.h
diff --git a/content/browser/payments/payment_manager.h b/content/browser/payments/payment_manager.h
index fa66185f1842da3d015bd3c45997a5b603cffafe..b0aa75b2c46964afeb13f9e53cdaf34dadceaeed 100644
--- a/content/browser/payments/payment_manager.h
+++ b/content/browser/payments/payment_manager.h
@@ -39,16 +39,18 @@ class CONTENT_EXPORT PaymentManager
   void DeletePaymentInstrument(
       const std::string& instrument_key,
       const DeletePaymentInstrumentCallback& callback) override;
-  void SetPaymentInstrument(
+  void GetPaymentInstrument(
       const std::string& instrument_key,
-      payments::mojom::PaymentInstrumentPtr details,
-      const SetPaymentInstrumentCallback& callback) override;
+      const GetPaymentInstrumentCallback& callback) override;
+  void KeysOfPaymentInstruments(
+      const KeysOfPaymentInstrumentsCallback& callback) override;
   void HasPaymentInstrument(
       const std::string& instrument_key,
       const HasPaymentInstrumentCallback& callback) override;
-  void GetPaymentInstrument(
+  void SetPaymentInstrument(
       const std::string& instrument_key,
-      const GetPaymentInstrumentCallback& callback) override;
+      payments::mojom::PaymentInstrumentPtr details,
+      const SetPaymentInstrumentCallback& callback) override;
 
   // Called when an error is detected on binding_.
   void OnConnectionError();