[NTP::Push] Add the classes for sending a breaking news subscription request

components/ntp_snippets/breaking_news/subscription_json_request.h

+// Copyright 2017 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 COMPONENTS_NTP_SNIPPETS_BREAKING_NEWS_SUBSCRIPTION_JSON_REQUEST_H_
+#define COMPONENTS_NTP_SNIPPETS_BREAKING_NEWS_SUBSCRIPTION_JSON_REQUEST_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "components/ntp_snippets/status.h"
+#include "components/translate/core/browser/language_model.h"
+#include "google_apis/gaia/oauth2_token_service.h"
+#include "net/http/http_request_headers.h"
+
+namespace ntp_snippets {
+
+namespace internal {
+
+// A single request to subscribe for breaking news via GCM.

[fhorschig, 2017/06/01 16:25:21]

nit: Please mention that the Request has to stay alive in order to
be successfully completed. Consider renaming it to fetcher.

[mamir, 2017/06/01 17:13:00]

Done.

+class SubscriptionJsonRequest : public net::URLFetcherDelegate {
+ public:
+  // A client can expect a message in the status only, if there was any error
+  // during the subscription. In successful cases, it will be an empty string.
+  using CompletedCallback =
+      base::OnceCallback<void(const ntp_snippets::Status& status)>;
+
+  // Builds non-authenticated SubscriptionJsonRequests.
+  class Builder {
+   public:
+    Builder();
+    Builder(Builder&&);
+    ~Builder();
+
+    // Builds a Request object that contains all data to fetch new snippets.
+    std::unique_ptr<SubscriptionJsonRequest> Build() const;
+
+    Builder& SetToken(const std::string& token);
+    Builder& SetUrl(const GURL& url);
+    Builder& SetUrlRequestContextGetter(
+        const scoped_refptr<net::URLRequestContextGetter>& context_getter);
+
+   private:
+    std::string BuildHeaders() const;
+    std::string BuildBody() const;
+    std::unique_ptr<net::URLFetcher> BuildURLFetcher(
+        net::URLFetcherDelegate* request,
+        const std::string& headers,
+        const std::string& body) const;
+
+    // GCM subscribtion token obtain from GCM driver (instanceID::getToken())
+    std::string token_;
+    // TODO(mamir): Additional fields to be added: country, language
+
+    GURL url_;
+    scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
+
+    // Optional properties.
+    std::string obfuscated_gaia_id_;

[fhorschig, 2017/06/01 16:25:21]

This property is very optional as it's never used. Remove?

[mamir, 2017/06/01 17:13:00]

Done.

+  };
+
+  ~SubscriptionJsonRequest() override;
+
+  void Start(CompletedCallback callback);

[fhorschig, 2017/06/01 16:25:21]

Could you comment this please?
(Something like: 
Starts a async request.
Invokes the callback when succeeded, failed or destroyed.)

[mamir, 2017/06/01 17:13:00]

Done.

+
+ private:
+  friend class Builder;
+  SubscriptionJsonRequest();
+  // URLFetcherDelegate implementation.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // The fetcher for subscribing.
+  std::unique_ptr<net::URLFetcher> url_fetcher_;
+
+  // The callback to notify when URLFetcher finished and results are available.

[fhorschig, 2017/06/01 16:25:21]

Nit: When the request is finished/aborted/destroyed. You call in in the dtor!

[mamir, 2017/06/01 17:13:00]

Done.

+  CompletedCallback request_completed_callback_;
+
+  base::WeakPtrFactory<SubscriptionJsonRequest> weak_ptr_factory_;

[fhorschig, 2017/06/01 16:25:21]

unused

[mamir, 2017/06/01 17:13:00]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(SubscriptionJsonRequest);
+};
+
+}  // namespace internal
+
+}  // namespace ntp_snippets
+
+#endif  // COMPONENTS_NTP_SNIPPETS_BREAKING_NEWS_SUBSCRIPTION_JSON_REQUEST_H_