Revert of NTP Zombie Code Slayer Part IV: Most Visited

chrome/browser/ui/webui/ntp/thumbnail_source.h

+// Copyright (c) 2012 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_NTP_THUMBNAIL_SOURCE_H_
+#define CHROME_BROWSER_UI_WEBUI_NTP_THUMBNAIL_SOURCE_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "content/public/browser/url_data_source.h"
+
+class Profile;
+
+namespace base {
+class RefCountedMemory;
+}
+
+namespace thumbnails {
+class ThumbnailService;
+}
+
+// ThumbnailSource is the gateway between network-level chrome: requests for
+// thumbnails and the history/top-sites backend that serves these.
+class ThumbnailSource : public content::URLDataSource {
+ public:
+  ThumbnailSource(Profile* profile, bool capture_thumbnails);
+
+  // 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& path) const override;
+  base::MessageLoop* MessageLoopForRequestPath(
+      const std::string& path) const override;
+  bool ShouldServiceRequest(const net::URLRequest* request) const override;
+
+ private:
+  ~ThumbnailSource() override;
+
+  // Raw PNG representation of the thumbnail to show when the thumbnail
+  // database doesn't have a thumbnail for a webpage.
+  scoped_refptr<base::RefCountedMemory> default_thumbnail_;
+
+  // ThumbnailService.
+  scoped_refptr<thumbnails::ThumbnailService> thumbnail_service_;
+
+  // Indicate that, when a URL for which we don't have a thumbnail is requested
+  // from this source, then Chrome should capture a thumbnail next time it
+  // navigates to this URL. This is useful when the thumbnail URLs are generated
+  // by an external service rather than TopSites, so Chrome can learn about the
+  // URLs for which it should get thumbnails. Sources that capture thumbnails
+  // are also be more lenient when matching thumbnail URLs by checking for
+  // existing thumbnails in the database that contain a URL matching the prefix
+  // of the requested URL.
+  const bool capture_thumbnails_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThumbnailSource);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_NTP_THUMBNAIL_SOURCE_H_