Give SelectFaviconFrames a quality score.

chrome/browser/favicon/select_favicon_frames.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_FAVICON_SELECT_FAVICON_FRAMES_H_
 #define CHROME_BROWSER_FAVICON_SELECT_FAVICON_FRAMES_H_
 
 #include <vector>
 
 #include "ui/base/layout.h"
 
 class SkBitmap;
 
 namespace gfx {
 class ImageSkia;
 }
 
 // Takes a list of all bitmaps found in a .ico file, and creates an
 // ImageSkia that's desired_size x desired_size pixels big. This
 // function adds a representation at every desired scale factor.
 // If desired_size is 0, the largest bitmap is returned unmodified.
+// If score is non-NULL, it receive a score between 0 (bad) and 1 (good)
+// that describes how well |bitmaps| were able to produce an image at
+// |desired_size| for |scale_factors|.
+// The score is arbitrary, but it's best for exact size matches,
+// and gets worse the more resampling needs to happen..
 gfx::ImageSkia SelectFaviconFrames(
     const std::vector<SkBitmap>& bitmaps,
     const std::vector<ui::ScaleFactor>& scale_factors,
-    int desired_size);
+    int desired_size,
+    float* score);
 
 #endif  // CHROME_BROWSER_FAVICON_SELECT_FAVICON_FRAMES_H_