Add support for pulling icons for OfflineItems

components/offline_items_collection/core/android/java/src/org/chromium/components/offline_items_collection/VisualsCallback.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;
+
+/**
+ * This interface is a Java counterpart to the C++ base::Callback meant to be used in response
+ * to {@link OfflineItemVisuals} requests.
+ */
+public 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);
+}