[Remote suggestions] Refactor the scheduler

components/ntp_snippets/remote/remote_suggestions_scheduler.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 COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_H_
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_H_
 
 #include "base/macros.h"
 
 namespace ntp_snippets {
 
-// Interface for informing the scheduler.
+class RemoteSuggestionsProvider;
+struct Status;
+
+// The scheduler for background fetching of remote suggestions has two callers:
+//  a) The actual provider that implements the fetching informs the scheduler
+//     about relevant events and changes in its state.
+//  b) External parties (such as the UI) that need to inform the scheduler about
+//     their events.
 class RemoteSuggestionsScheduler {
  public:
-  // Internal triggers to consider fetching content suggestions.
+  // Set the provider that performs background fetching. Should be only called
+  // by the factory.
+  virtual void SetProvider(RemoteSuggestionsProvider* provider) = 0;
+
+  // ***** Internal triggers to consider fetching content suggestions. *****
 
   // Called whenever the remote suggestions provider becomes active (on startup,
   // or later on).
   virtual void OnProviderActivated() = 0;
 
   // Called whenever the remote suggestions provider becomes inactive (on
   // startup, or later on).
   virtual void OnProviderDeactivated() = 0;
 
   // Called whenever the remote suggestions provider clears all suggestions.
   virtual void OnSuggestionsCleared() = 0;
 
   // Called whenever the remote suggestions provider clears all suggestions
   // because history gets cleared (and we must not show them any more).
   virtual void OnHistoryCleared() = 0;
 
-  // External triggers to consider fetching content suggestions.
+  // Returns true if quota is available for another request.
+  virtual bool AcquireQuotaForInteractiveFetch() = 0;
+
+  // Called whenever the remote suggestions provider finishes an interactive
+  // fetch (with provided |fetch_status|).
+  virtual void OnInteractiveFetchFinished(Status fetch_status) = 0;
+
+  // ***** External triggers to consider fetching content suggestions. *****
 
   // Called whenever chrome is started warm or the user switches to Chrome.
   virtual void OnBrowserForegrounded() = 0;
 
   // Called whenever chrome is cold started.
   // To keep start ups fast, defer any work possible.
   virtual void OnBrowserColdStart() = 0;
 
   // Called whenever a new NTP is opened. This may be called on cold starts.
   // So to keep start ups fast, defer heavy work for cold starts.
   virtual void OnNTPOpened() = 0;
 
   // Fetch content suggestions.
   virtual void OnPersistentSchedulerWakeUp() = 0;
 
   // Force rescheduling of fetching.
   virtual void RescheduleFetching() = 0;
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_H_