PaymentApp: Add PaymentAppProvider class.

content/public/browser/payment_app_provider.h

+// 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_PAYMENT_APP_PROVIDER_H_
+#define CONTENT_PUBLIC_BROWSER_PAYMENT_APP_PROVIDER_H_
+
+#include <utility>
+#include <vector>
+
+#include "base/callback_forward.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class BrowserContext;
+
+// This is providing the service worker based payment app related APIs to
+// Chrome layer. This class is a singleton, the instance of which can be
+// retrieved using the static GetInstance() method.
+// All methods must be called on the UI thread.
+class CONTENT_EXPORT PaymentAppProvider {
+ public:
+  // This static function is actually implemented in PaymentAppProviderImpl.cc.
+  // Please see: content/browser/payments/payment_app_provider_impl.cc
+  static PaymentAppProvider* GetInstance();
+
+  // The ManifestWithID is a pair of the service worker registration id and
+  // the payment app manifest data associated with it.
+  using ManifestWithID =
+      std::pair<int64_t, payments::mojom::PaymentAppManifestPtr>;
+  using Manifests = std::vector<ManifestWithID>;
+  using GetAllManifestsCallback = base::Callback<void(Manifests)>;
+
+  // Should be accessed only on the UI thread.
+  virtual void GetAllManifests(BrowserContext* browser_context,
+                               const GetAllManifestsCallback& callback) = 0;
+
+ protected:
+  virtual ~PaymentAppProvider() {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_PAYMENT_APP_PROVIDER_H_