PaymentApp: Implement PaymentAppManager.setManifest().

content/browser/payments/payment_app.proto

Index: content/browser/payments/payment_app.proto
diff --git a/content/browser/payments/payment_app.proto b/content/browser/payments/payment_app.proto
new file mode 100644
index 0000000000000000000000000000000000000000..3c740884c0ab2cec002aea0968963107d26b194a
--- /dev/null
+++ b/content/browser/payments/payment_app.proto
@@ -0,0 +1,22 @@
+// 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 PaymentAppManifestProto {
+  required string label = 1;
+  optional string icon = 2;
+  repeated PaymentAppOptionProto options = 3;
+}
+
+message PaymentAppOptionProto {
+  required string label = 1;
+  optional string icon = 2;
+  required string id = 3;
+  repeated string enabled_methods = 4;
+}