Move thumbnail to history component

chrome/common/thumbnail_score.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_COMMON_THUMBNAIL_SCORE_H_
-#define CHROME_COMMON_THUMBNAIL_SCORE_H_
-
-#include <string>
-#include "base/time/time.h"
-
-// A set of metadata about a Thumbnail.
-struct ThumbnailScore {
-  // Initializes the ThumbnailScore to the absolute worst possible values
-  // except for time, which is set to Now(), and redirect_hops_from_dest which
-  // is set to 0.
-  ThumbnailScore();
-
-  // Builds a ThumbnailScore with the passed in values, and sets the
-  // thumbnail generation time to Now().
-  ThumbnailScore(double score, bool clipping, bool top);
-
-  // Builds a ThumbnailScore with the passed in values.
-  ThumbnailScore(double score, bool clipping, bool top,
-                 const base::Time& time);
-  ~ThumbnailScore();
-
-  // Tests for equivalence between two ThumbnailScore objects.
-  bool Equals(const ThumbnailScore& rhs) const;
-
-  // Returns string representation of this object.
-  std::string ToString() const;
-
-  // How "boring" a thumbnail is. The boring score is the 0,1 ranged
-  // percentage of pixels that are the most common luma. Higher boring
-  // scores indicate that a higher percentage of a bitmap are all the
-  // same brightness (most likely the same color).
-  //
-  // The score should only be used for comparing two thumbnails taken from
-  // the same page to see which one is more boring/interesting. The
-  // absolute score is not suitable for judging whether the thumbnail is
-  // actually boring or not. For instance, www.google.com is very
-  // succinct, so the boring score can be as high as 0.9, depending on the
-  // browser window size.
-  double boring_score;
-
-  // Whether the thumbnail was taken with height greater than
-  // width or width greater than height and the aspect ratio less than
-  // kTooWideAspectRatio. In cases where we don't have |good_clipping|,
-  // the thumbnails are either clipped from the horizontal center of the
-  // window, or are otherwise weirdly stretched.
-  bool good_clipping;
-
-  // Whether this thumbnail was taken while the renderer was
-  // displaying the top of the page. Most pages are more recognizable
-  // by their headers then by a set of random text half way down the
-  // page; i.e. most MediaWiki sites would be indistinguishable by
-  // thumbnails with |at_top| set to false.
-  bool at_top;
-
-  // Whether this thumbnail was taken after load was completed.
-  // Thumbnails taken while page loading may only contain partial
-  // contents.
-  bool load_completed;
-
-  // Record the time when a thumbnail was taken. This is used to make
-  // sure thumbnails are kept fresh.
-  base::Time time_at_snapshot;
-
-  // The number of hops from the final destination page that this thumbnail was
-  // taken at. When a thumbnail is taken, this will always be the redirect
-  // destination (value of 0).
-  //
-  // For the most visited view, we'll sometimes get thumbnails for URLs in the
-  // middle of a redirect chain. In this case, the top sites component will set
-  // this value so the distance from the destination can be taken into account
-  // by the comparison function.
-  //
-  // If "http://google.com/" redirected to "http://www.google.com/", then
-  // a thumbnail for the first would have a redirect hop of 1, and the second
-  // would have a redirect hop of 0.
-  int redirect_hops_from_dest;
-
-  // How bad a thumbnail needs to be before we completely ignore it.
-  static const double kThumbnailMaximumBoringness;
-
-  // We consider a thumbnail interesting enough if the boring score is
-  // lower than this.
-  static const double kThumbnailInterestingEnoughBoringness;
-
-  // Time before we take a worse thumbnail (subject to
-  // kThumbnailMaximumBoringness) over what's currently in the database
-  // for freshness.
-  static const int64 kUpdateThumbnailTimeDays;
-
-  // Penalty of how much more boring a thumbnail should be per hour.
-  static const double kThumbnailDegradePerHour;
-
-  // If a thumbnail is taken with the aspect ratio greater than or equal to
-  // this value, |good_clipping| is to false.
-  static const double kTooWideAspectRatio;
-
-  // Checks whether we should consider updating a new thumbnail based on
-  // this score. For instance, we don't have to update a new thumbnail
-  // if the current thumbnail is new and interesting enough.
-  bool ShouldConsiderUpdating();
-};
-
-// Checks whether we should replace one thumbnail with another.
-bool ShouldReplaceThumbnailWith(const ThumbnailScore& current,
-                                const ThumbnailScore& replacement);
-
-#endif  // CHROME_COMMON_THUMBNAIL_SCORE_H_