[Remote suggestions] Move the throttler into the Scheduler

components/ntp_snippets/remote/remote_suggestions_provider.h

 // Copyright 2015 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_REMOTE_REMOTE_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_PROVIDER_H_
 
 #include <memory>
 
 #include "base/callback_forward.h"
@@ skipping 14 matching lines @@
   using FetchStatusCallback = base::Callback<void(Status status_code)>;
 
   ~RemoteSuggestionsProvider() override;
 
   // Fetches suggestions from the server for all remote categories and replaces
   // old suggestions by the new ones. The request to the server is performed as
   // an background request. Background requests are used for actions not
   // triggered by the user and have lower priority on the server. After the
   // fetch finished, the provided |callback| will be triggered with the status
   // of the fetch (unless nullptr).
+  // TODO(jkrcal): Change to FetchStatusCallback callback as callbacks already
+  // have is_empty() functionality. crbug.com/676317
   virtual void RefetchInTheBackground(
       std::unique_ptr<FetchStatusCallback> callback) = 0;
 
   virtual const RemoteSuggestionsFetcher* suggestions_fetcher_for_debugging()
       const = 0;
 
  protected:
   RemoteSuggestionsProvider(Observer* observer);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_PROVIDER_H_