[Payments] Implement payment instrument icons

content/browser/payments/payment_app.proto

 // Copyright 2016 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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package content;
 
 message StoredPaymentInstrumentKeyInfoProto {
   optional uint64 insertion_order = 1;
   optional string key = 2;
 }
 
+message StoredPaymentInstrumentImageObject {
+  optional string src = 1;
+}
+
 message StoredPaymentInstrumentProto {
   optional int64 registration_id = 1;
   optional string instrument_key = 2;
   optional string origin = 3;
   optional string name = 4;
   repeated string enabled_methods = 5;
   optional string stringified_capabilities = 6;
+  repeated StoredPaymentInstrumentImageObject icons = 7;
+  optional string decoded_instrument_icon = 8;
 }