PaymentApp: Add interfaces for implementing InvokePaymentApp().

components/payments/BUILD.gn

 # 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("payment_request") {
   sources = [
     "payment_request.mojom",
   ]
 
   public_deps = [
     "//mojo/common:common_custom_types",
   ]
 }
 
 mojom("payment_app") {
   sources = [
     "payment_app.mojom",
   ]
 
   public_deps = [
+    ":payment_request",
     "//mojo/common:common_custom_types",
   ]
 }
 
 static_library("payment_validation") {
   sources = [
     "payment_details_validation.cc",
     "payment_details_validation.h",
     "payments_validators.cc",
     "payments_validators.h",
@@ skipping 11 matching lines @@
   testonly = true
   sources = [
     "payments_validators_test.cc",
   ]
 
   deps = [
     ":payment_validation",
     "//testing/gtest",
   ]
 }