[Icons NTP] Add chrome://large-icon host, which resizes icon and renders fallback.

chrome/browser/ui/webui/large_icon_source.h

+// Copyright 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 CHROME_BROWSER_UI_WEBUI_LARGE_ICON_SOURCE_H_
+#define CHROME_BROWSER_UI_WEBUI_LARGE_ICON_SOURCE_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/task/cancelable_task_tracker.h"
+#include "components/favicon_base/fallback_icon_service.h"
+#include "components/favicon_base/favicon_types.h"
+#include "content/public/browser/url_data_source.h"
+
+class Profile;
+
+// LargeIconSource services explicit chrome:// requests for large icons.
+//
+// Format:
+//   chrome://large-icon/size/url
+// All of the parameters except for the url are optional. However, the order of

[Roger McFarlane (Chromium), 2015/03/17 20:41:01]

abortive comment?

[huangs, 2015/03/18 22:54:12]

Done.

+//
+// Parameter:
+//  'size'
+//    Positive integer to specify the large icon's size in pixels.
+//  'url'
+//    String to specify the page URL of the large icon.
+//
+//  Example: chrome://large-icon/48/http://www.google.com/
+//    This requests a 48x48 large icon for http://www.google.com.
+class LargeIconSource : public content::URLDataSource {
+ public:
+  explicit LargeIconSource(Profile* profile);
+
+  ~LargeIconSource() override;
+
+  // content::URLDataSource implementation.
+  std::string GetSource() const override;
+  void StartDataRequest(
+      const std::string& path,
+      int render_process_id,
+      int render_frame_id,
+      const content::URLDataSource::GotDataCallback& callback) override;
+  std::string GetMimeType(const std::string&) const override;
+  bool ShouldReplaceExistingSource() const override;
+  bool ShouldServiceRequest(const net::URLRequest* request) const override;
+
+ protected:
+  struct IconRequest {
+    IconRequest();
+    IconRequest(const content::URLDataSource::GotDataCallback& callback_in,
+                const GURL& path_in,
+                int size_in);
+    ~IconRequest();
+
+    content::URLDataSource::GotDataCallback callback;
+    GURL url;
+    int size;
+  };
+
+ private:
+  // Callback for icon data retrieval request.
+  void OnIconDataAvailable(
+      const IconRequest& request,
+      const favicon_base::FaviconRawBitmapResult& bitmap_result);
+
+  // Handler for icon retrieval and resizing errors. If
+  // |render_fallback_on_failure_| then sends fallback icon, otherwise send
+  // "Not Found" response.
+  void OnIconDataError(const IconRequest& request);
+
+  // Renders and returns a fallback icon.

[beaudoin, 2015/03/17 23:08:36]

I don't like "returns" here since the method doesn't return anything. I would
use: "invokes the request callback with..." 

[huangs, 2015/03/18 22:54:12]

Replacing "returns" with "sends".  It's shorter, and is also used above.

[beaudoin, 2015/03/19 01:50:18]

Acknowledged.

+  void SendFallbackIcon(const IconRequest& request);
+
+  // Returns null to trigger "Not Found" response.
+  void SendNotFoundResponse(
+      const content::URLDataSource::GotDataCallback& callback);
+
+  Profile* profile_;
+
+  base::CancelableTaskTracker cancelable_task_tracker_;
+
+  scoped_ptr<favicon_base::FallbackIconService> fallback_icon_service_;
+
+  // Flag to control what to do when large icon lookup fails.
+  bool render_fallback_on_failure_;
+
+  DISALLOW_COPY_AND_ASSIGN(LargeIconSource);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_LARGE_ICON_SOURCE_H_