[Icons NTP] Refactor large_icon_source to extract the logic shared between desktop and Android to f…

components/favicon_base/fallback_icon_style.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 COMPONENTS_FAVICON_BASE_FALLBACK_ICON_STYLE_H_
 #define COMPONENTS_FAVICON_BASE_FALLBACK_ICON_STYLE_H_
 
+#include "base/memory/ref_counted_memory.h"
 #include "third_party/skia/include/core/SkColor.h"
 
 namespace favicon_base {
 
 // Styling specifications of a fallback icon. The icon is composed of a solid
 // rounded square containing a single letter. The specification excludes the
 // icon URL and size, which are given when the icon is rendered.
 struct FallbackIconStyle {
   FallbackIconStyle();
   ~FallbackIconStyle();
@@ skipping 12 matching lines @@
   // The roundness of the icon's corners. 0 => square icon, 1 => circle icon.
   double roundness;
 };
 
 // Reassigns |style|'s |text_color| to matches well against |background_color|.
 void MatchFallbackIconTextColorAgainstBackgroundColor(FallbackIconStyle* style);
 
 // Returns whether |style| values are within bounds.
 bool ValidateFallbackIconStyle(const FallbackIconStyle& style);
 
+// Set |style|'s background color to the dominant color of |bitmap_data|,
+// clamping luminance down to a reasonable maximum value so that light text is
+// readable.
+void SetDominantColorAsBackground(
+    const scoped_refptr<base::RefCountedMemory>& bitmap_data,
+    FallbackIconStyle* style);
+
 }  // namespace favicon_base
 
 #endif  // COMPONENTS_FAVICON_BASE_FALLBACK_ICON_STYLE_H_