Make GetDismissedSuggestionsForDebugging asynchronous

components/ntp_snippets/content_suggestions_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 COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 12 matching lines @@
 // Provides content suggestions from one particular source.
 // A provider can provide suggestions for multiple ContentSuggestionCategories,
 // but for every category that it provides, it will be the only provider in the
 // system which provides suggestions for that category.
 // Providers are created by the ContentSuggestionsServiceFactory and owned and
 // shut down by the ContentSuggestionsService.
 class ContentSuggestionsProvider {
  public:
   using ImageFetchedCallback =
       base::Callback<void(const std::string& suggestion_id, const gfx::Image&)>;
+  using DismissedSuggestionsCallback = base::Callback<void(
+      std::vector<ContentSuggestion> dismissed_suggestions)>;
 
   // The observer of a provider is notified when new data is available.
   class Observer {
    public:
     // Called when the available content changed.
     // If a provider provides suggestions for multiple categories, this callback
     // is called once per category. The |suggestions| parameter always contains
     // the full list of currently available suggestions for that category, i.e.,
     // an empty list will remove all suggestions from the given category. Note
     // that to clear them from the UI immediately, the provider needs to change
@@ skipping 65 matching lines @@
   virtual void FetchSuggestionImage(const std::string& suggestion_id,
                                     const ImageFetchedCallback& callback) = 0;
 
   // Used only for debugging purposes. Clears all caches for the given category,
   // so that the next fetch starts from scratch.
   virtual void ClearCachedSuggestionsForDebugging(Category category) = 0;
 
   // Used only for debugging purposes. Retrieves suggestions for the given
   // |category| that have previously been dismissed and are still stored in the
   // provider. If the provider doesn't store dismissed suggestions for the given
-  // |category|, it always returns an empty vector.
-  virtual std::vector<ContentSuggestion> GetDismissedSuggestionsForDebugging(
-      Category category) = 0;
+  // |category|, it always calls the callback with an empty vector. The callback
+  // may be called synchronously.
+  virtual void GetDismissedSuggestionsForDebugging(
+      Category category,
+      const DismissedSuggestionsCallback& callback) = 0;
 
   // Used only for debugging purposes. Clears the cache of dismissed
   // suggestions for the given |category|, if present, so that no suggestions
   // are suppressed. This does not necessarily make previously dismissed
   // suggestions reappear, as they may have been permanently deleted, depending
   // on the provider implementation.
   virtual void ClearDismissedSuggestionsForDebugging(Category category) = 0;
 
  protected:
   ContentSuggestionsProvider(Observer* observer,
@@ skipping 16 matching lines @@
   CategoryFactory* category_factory() const { return category_factory_; }
 
  private:
   Observer* observer_;
   CategoryFactory* category_factory_;
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_