[Remote suggestions] Move all decisions to fetch to 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 RemoteSuggestionsScheduler {
  public:
+  // 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.
 
   // 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_