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

components/favicon_base/fallback_icon_style.h

Index: components/favicon_base/fallback_icon_style.h
diff --git a/components/favicon_base/fallback_icon_style.h b/components/favicon_base/fallback_icon_style.h
index 097636b0ccb522aacb2af8aaa0612dfe70afe53d..84842edd7e1765bf52bde9dbc229aed9b6358831 100644
--- a/components/favicon_base/fallback_icon_style.h
+++ b/components/favicon_base/fallback_icon_style.h
@@ -5,6 +5,7 @@
 #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 {
@@ -37,6 +38,13 @@ 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_