[NTP Snippets] Pass "no suggestions" message from the backend to the UI

components/ntp_snippets/category_info.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_CATEGORY_INFO_H_
 #define COMPONENTS_NTP_SNIPPETS_CATEGORY_INFO_H_
 
 #include "base/macros.h"
 #include "base/strings/string16.h"
 
 namespace ntp_snippets {
 
 // On Android builds, a Java counterpart will be generated for this enum.
 // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.chrome.browser.ntp.snippets
 enum class ContentSuggestionsCardLayout {
   // Uses all fields.
   FULL_CARD,
 
   // No snippet_text and no thumbnail image.
   MINIMAL_CARD
 };
 
 // Contains static meta information about a Category.
 class CategoryInfo {
  public:
   CategoryInfo(const base::string16& title,
                ContentSuggestionsCardLayout card_layout,
                bool has_more_button,
-               bool show_if_empty);
+               bool show_if_empty,
+               const base::string16& no_suggestions_message);
   CategoryInfo(CategoryInfo&&) = default;
   CategoryInfo& operator=(CategoryInfo&&) = default;
 
   ~CategoryInfo();
 
   // Localized title of the category.
   const base::string16& title() const { return title_; }
 
   // Layout of the cards to be used to display suggestions in this category.
   ContentSuggestionsCardLayout card_layout() const { return card_layout_; }
 
-  // Whether the category supports a "More" button. The button either triggers
-  // a fixed action (like opening a native page) or, if there is no such fixed
-  // action, it queries the provider for more suggestions.
+  // Whether the category should show a "More" button even if it's not empty
+  // (there's always a "More" or "Reload" button if it is empty). The button
+  // either triggers a fixed action (like opening a native page) or, if there
+  // is no such fixed action, it queries the provider for more suggestions.
+  // TODO(treib): Rename this to "always_show_more_button".
   bool has_more_button() const { return has_more_button_; }
 
   // Whether this category should be shown if it offers no suggestions.
   bool show_if_empty() const { return show_if_empty_; }
 
+  // The message to show if there are no suggestions in this category. Note that
+  // this matters even if |show_if_empty()| is false: The message still shows
+  // up when the user dismisses all suggestions in the category.
+  const base::string16& no_suggestions_message() const {
+    return no_suggestions_message_;
+  }
+
  private:
   base::string16 title_;
   ContentSuggestionsCardLayout card_layout_;
   bool has_more_button_;
   bool show_if_empty_;
+  base::string16 no_suggestions_message_;
 
   DISALLOW_COPY_AND_ASSIGN(CategoryInfo);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CATEGORY_INFO_H_