webapps: allow callers of icon downloader/selector to specify a minimum size

chrome/browser/manifest/manifest_icon_selector.cc

 // 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.
 
 #include "chrome/browser/manifest/manifest_icon_selector.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 
@@ skipping 146 matching lines @@
     }
   }
 
   return result;
 }
 
 // static
 GURL ManifestIconSelector::FindBestMatchingIcon(
     const std::vector<Manifest::Icon>& unfiltered_icons,
     const float preferred_icon_size_in_dp,
+    const float minimum_icon_size_in_dp,
     const gfx::Screen* screen) {
   const float device_scale_factor =
       screen->GetPrimaryDisplay().device_scale_factor();
   const float preferred_icon_size_in_pixels =
       preferred_icon_size_in_dp * device_scale_factor;
-
-  const int minimum_scale_factor = std::max(
-      static_cast<int>(floor(device_scale_factor - 1)), 1);
   const float minimum_icon_size_in_pixels =
-      preferred_icon_size_in_dp * minimum_scale_factor;
+      minimum_icon_size_in_dp * device_scale_factor;
 
   std::vector<Manifest::Icon> icons =
       ManifestIconSelector::FilterIconsByType(unfiltered_icons);
 
   ManifestIconSelector selector(preferred_icon_size_in_pixels,
                                 minimum_icon_size_in_pixels);
   int index = selector.FindBestMatchingIcon(icons, device_scale_factor);
   if (index == -1)
     return GURL();
   return icons[index].src;
 }