Add support for pulling icons for OfflineItems

components/offline_items_collection/core/offline_content_provider.h

 // 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.
 
 #ifndef COMPONENTS_OFFLINE_ITEMS_COLLETION_CORE_OFFLINE_CONTENT_PROVIDER_H_
 #define COMPONENTS_OFFLINE_ITEMS_COLLETION_CORE_OFFLINE_CONTENT_PROVIDER_H_
 
 #include <string>
 #include <vector>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "url/gurl.h"
 
 namespace offline_items_collection {
 
 struct ContentId;
 struct OfflineItem;
+struct OfflineItemVisuals;
 
 // A provider of a set of OfflineItems that are meant to be exposed to the UI.
 // The provider is required to notify all observers of OnItemsAvailable when the
 // underlying data set is initialized.  Without that call it should not expect
 // nor have to support any other calls to this provider.
 class OfflineContentProvider {
  public:
   using OfflineItemList = std::vector<OfflineItem>;
+  using VisualsCallback =
+      base::Callback<void(const ContentId&, const OfflineItemVisuals*)>;
 
   // An observer class that should be notified of relevant changes to the
   // underlying data source.
   class Observer {
    public:
     // Called when the underlying data source for the provider has been
     // initialized and the contents are able to be queried and interacted with.
     // |provider| should be a reference to this OfflineContentProvider that is
     // initialized.
     virtual void OnItemsAvailable(OfflineContentProvider* provider) = 0;
 
     // Called when one or more OfflineItems have been added and should be shown
     // in the UI.
     virtual void OnItemsAdded(const OfflineItemList& items) = 0;
 
     // Called when the OfflineItem represented by |id| should be removed from
     // the UI.
     virtual void OnItemRemoved(const ContentId& id) = 0;
 
     // Called when the contents of |item| have been updated and the UI should be
     // refreshed for that item.
+    // TODO(dtrainor): Make this take a list of OfflineItems.
     virtual void OnItemUpdated(const OfflineItem& item) = 0;
 
    protected:
     virtual ~Observer() = default;
   };
 
   // Returns whether or not the underlying data source for this provider has
   // been initialized and is ready to start returning content.  This provider
   // should not need to support handling the other data query/manipulation
   // methods if this returns false.
@@ skipping 15 matching lines @@
   virtual void ResumeDownload(const ContentId& id) = 0;
 
   // Returns an OfflineItem represented by |id| or |nullptr| if none exists.
   // The caller should not hold ownership of the returned item beyond the scope
   // of the function call.
   virtual const OfflineItem* GetItemById(const ContentId& id) = 0;
 
   // Returns all OfflineItems for this particular provider.
   virtual OfflineItemList GetAllItems() = 0;
 
+  // Asks for an OfflineItemVisuals struct for an OfflineItem represented by
+  // |id| or |nullptr| if one doesn't exist.  The caller should post any

[nyquist, 2017/04/13 05:08:25]

The "caller"? Do you mean the implementor of the interface?

[David Trainor- moved to gerrit, 2017/04/13 07:20:23]

Ah yeah sorry thanks!

+  // replies even if the results are available immediately to prevent reentrancy
+  // and for consistent behavior.
+  virtual void GetVisualsForItem(const ContentId& id,
+                                 const VisualsCallback& callback) = 0;
+
   // Adds an observer that should be notified of OfflineItem list modifications.
   // If the provider is already initialized OnItemsAvailable should be scheduled
   // on this observer (suggested over calling the method directly to avoid
   // reentrancy).
   virtual void AddObserver(Observer* observer) = 0;
 
   // Removes an observer.  No further notifications should be sent to it.
   virtual void RemoveObserver(Observer* observer) = 0;
 
  protected:
   virtual ~OfflineContentProvider() = default;
 };
 
 }  // namespace offline_items_collection
 
 #endif  // COMPONENTS_OFFLINE_ITEMS_COLLETION_CORE_OFFLINE_CONTENT_PROVIDER_H_