Support action button to fetch more content suggestions

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 63 matching lines @@
   // categories, and through |OnCategoryStatusChanged| with parameter
   // NOT_PROVIDED for removed categories.
   virtual std::vector<Category> GetProvidedCategories() = 0;
 
   // Determines the status of the given |category|, see CategoryStatus.
   virtual CategoryStatus GetCategoryStatus(Category category) = 0;
 
   // Returns the meta information for the given |category|.
   virtual CategoryInfo GetCategoryInfo(Category category) = 0;
 
+  // Triggers a fetch for new suggestions (over the network, for example) for
+  // the given |category|. This must be initiated by the user (e.g. by clicking
+  // the a "More" button). New suggestions will become available through

[Marc Treib, 2016/08/10 09:40:31]

nit: remove "a"

[Philipp Keck, 2016/08/10 13:14:46]

Done.

+  // |Observer::OnNewSuggestions|.
+  virtual void FetchMoreSuggestions(Category category) = 0;

[Marc Treib, 2016/08/10 09:40:31]

Hm. For now, we don't expect this method to ever actually get called, right? All
the "more" buttons we'll have in M54 will have special UI actions. Might have
been better to leave this out until we actually need it.
But since you've already written it, and we're pretty sure we are actually gonna
need it, I guess might as well keep it now.

[Philipp Keck, 2016/08/10 13:14:46]

Acknowledged.

We could, instead, put sth. like a notreached in the else-branch here:
https://codereview.chromium.org/2232783002/diff/1/chrome/android/java/src/org...

But actually, I think we will need this: Our status cards will become
per-section (or are already). We will have a "All Read --> Reload" card under
the "Articles for you" header. In M55, this will be replaced with a "All Read,
nothing here" card and the usual "More" button under the status-empty-card. But
for M54, it's the Reload-button on the card. And instead of calling the static
FetchSnippets across the bridge, we might as well trigger the section-specific
FetchMoreSuggestion as it's supposed to be. (Although they end up in the same
place, effectively).

+
   // Dismisses the suggestion with the given ID. A provider needs to ensure that
   // a once-dismissed suggestion is never delivered again (through the
   // Observer). The provider must not call Observer::OnSuggestionsChanged if the
   // removal of the dismissed suggestion is the only change.
   virtual void DismissSuggestion(const std::string& suggestion_id) = 0;
 
   // Fetches the image for the suggestion with the given ID and returns it
   // through the callback. This fetch may occur locally or from the internet.
   // If that suggestion doesn't exist, doesn't have an image or if the fetch
   // fails, the callback gets a null image. The callback will not be called
@@ skipping 39 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_