PaymentApp: Implement PaymentAppManager.setManifest().

content/browser/payments/BUILD.gn

Index: content/browser/payments/BUILD.gn
diff --git a/content/browser/payments/BUILD.gn b/content/browser/payments/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..07e9bfa83958b1a770075eeea3a495fcb0cd7d3a
--- /dev/null
+++ b/content/browser/payments/BUILD.gn
@@ -0,0 +1,11 @@
+# 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("//third_party/protobuf/proto_library.gni")
+
+proto_library("payment_app_proto") {
+  sources = [
+    "payment_app.proto",
+  ]
+}