Add support for pulling icons for OfflineItems

components/offline_items_collection/core/android/java/src/org/chromium/components/offline_items_collection/OfflineContentProvider.java

 // Copyright 2017 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.
 
 package org.chromium.components.offline_items_collection;
 
+import android.support.annotation.Nullable;
+
 import java.util.ArrayList;
 
 /**
  * This interface is a Java counterpart to the C++ OfflineContentProvider
  * (components/offline_items_collection/core/offline_content_provider.h) class.
  */
 public interface OfflineContentProvider {
-    /** This interface is a Java counterpart to the C++ OfflineContentProvider::Observer
+    /**
+     * This interface is a Java counterpart to the C++ base::Callback meant to be used in response
+     * to {@link OfflineItemVisuals} requests.
+     */
+    interface VisualsCallback {
+        /**
+         * @param id      The {@link ContentId} that {@code visuals} is associated with.
+         * @param visuals The {@link OfflineItemVisuals}, if any, associated with {@code id}.
+         */
+        void onVisualsAvailable(ContentId id, @Nullable OfflineItemVisuals visuals);
+    }
+
+    /**
+     * This interface is a Java counterpart to the C++ OfflineContentProvider::Observer
      * (components/offline_items_collection/core/offline_content_provider.h) class.
      */
     interface Observer {
         /** See OfflineContentProvider::Observer::OnItemsAvailable(...). */
         void onItemsAvailable();
 
         /** See OfflineContentProvider::Observer::OnItemsAdded(...). */
         void onItemsAdded(ArrayList<OfflineItem> items);
 
         /** See OfflineContentProvider::Observer::OnItemRemoved(...). */
@@ skipping 20 matching lines @@
 
     /** See OfflineContentProvider::ResumeDownload(...). */
     void resumeDownload(ContentId id);
 
     /** See OfflineContentProvider::GetItemById(...). */
     OfflineItem getItemById(ContentId id);
 
     /** See OfflineContentProvider::GetAllItems(). */
     ArrayList<OfflineItem> getAllItems();
 
+    /** See OfflineContentProvider::GetVisualsForItem(...). */
+    void getVisualsForItem(ContentId id, VisualsCallback callback);
+
     /** See OfflineContentProvider::AddObserver(...). */
     void addObserver(Observer observer);
 
     /** See OfflineContentProvider::RemoveObserver(...). */
     void removeObserver(Observer observer);
 }