[Icons NTP] Refactor large_icon_source to extract the logic shared between desktop and Android to f…

components/favicon/core/large_icon_service.h

+// Copyright (c) 2015 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_FAVICON_CORE_LARGE_ICON_SERVICE_H_
+#define COMPONENTS_FAVICON_CORE_LARGE_ICON_SERVICE_H_
+
+#include <vector>
+
+#include "base/task/cancelable_task_tracker.h"
+#include "components/favicon_base/favicon_callback.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+class GURL;
+
+namespace favicon_base {
+struct FaviconRawBitmapResult;
+}
+
+namespace favicon {
+
+class FaviconService;
+
+// The large icon service provides methods to access large icons. It relies on
+// the favicon service.
+class LargeIconService : public KeyedService {
+ public:
+  LargeIconService(FaviconService* favicon_service);
+
+  ~LargeIconService() override;
+
+  // Requests the best large icon for the page at |page_url| given the requested
+  // |desired_size_in_pixel|. If no good large icon can be found, returns the
+  // fallback style to use, for which the background is set to the dominant
+  // color of a smaller icon when one is available.
+  base::CancelableTaskTracker::TaskId GetLargeIconOrFallbackStyle(
+    const GURL& page_url,
+    int desired_size_in_pixel,
+    const favicon_base::LargeIconCallback& callback,
+    base::CancelableTaskTracker* tracker);
+
+ private:
+  // Intermediate callback for GetLargeIconOrFallbackStyle(). Ensures the large
+  // icon is the desired size, if not compute the icon fallback style and use it
+  // to invoke |callback|.

[huangs, 2015/04/21 05:00:28]

I noticed that the "ensure the large icon is the desired size", i.e., resizing
large icon to match |desired_size_in_pixel|, is broken.  No need to fix this in
CL, but please update comments by removing the "Eusure..." and add add

// FIXME: Ensure large icon is the desired size.

Alternatively we can abandon the attempt to do resizing here. but then we'll
have to worry about:
- Ensuring chrome-search://large-icon is not usable by NTP (only allowed in
iframe).
- Verifying Android code will do the proper resizing at some point (I think it
does already).

[beaudoin, 2015/04/21 15:11:11]

Added TODO in large_icon_service.cc. Let's discuss if we want to resize it here
or in HTML later.

+  void RunLargeIconCallback(
+      const favicon_base::LargeIconCallback& callback,
+      int desired_size_in_pixel,
+      const favicon_base::FaviconRawBitmapResult& bitmap_result);
+
+  FaviconService* favicon_service_;
+
+  // A pre-populated list of the types of icon files to consider when looking
+  // for large icons. Note: this is simply an optimization over populating an
+  // icon type vector on each request.
+  std::vector<int> large_icon_types_;
+
+  DISALLOW_COPY_AND_ASSIGN(LargeIconService);
+};
+
+}  // namespace favicon
+
+#endif  // COMPONENTS_FAVICON_CORE_LARGE_ICON_SERVICE_H_