color_utils cleanup:

components/favicon_base/fallback_icon_style.cc

Index: components/favicon_base/fallback_icon_style.cc
diff --git a/components/favicon_base/fallback_icon_style.cc b/components/favicon_base/fallback_icon_style.cc
index 83305f71e12a48fd4b69ceffc93607f43b5961df..64ddf48e57ec7c8bcdeea76906a868cd7426b26b 100644
--- a/components/favicon_base/fallback_icon_style.cc
+++ b/components/favicon_base/fallback_icon_style.cc
@@ -13,14 +13,14 @@ namespace favicon_base {
 
 namespace {
 
-// Luminance threshold for background color determine whether to use dark or
-// light text color.
-const int kDarkTextLuminanceThreshold = 190;
+// Luma threshold for background color determine whether to use dark or light
+// text color.
+const uint8_t kDarkTextLumaThreshold = 190;
 
-// The maximum luminance of the background color to ensure light text is
+// The maximum lightness of the background color to ensure light text is
 // readable.
-const double kMaxBackgroundColorLuminance = 0.67;
-const double kMinBackgroundColorLuminance = 0.15;
+const double kMaxBackgroundColorLightness = 0.67;
+const double kMinBackgroundColorLightness = 0.15;
 
 // Default values for FallbackIconStyle.
 const SkColor kDefaultBackgroundColor = SkColorSetRGB(0x78, 0x78, 0x78);
@@ -51,9 +51,9 @@ bool FallbackIconStyle::operator==(const FallbackIconStyle& other) const {
 
 void MatchFallbackIconTextColorAgainstBackgroundColor(
     FallbackIconStyle* style) {
-  int luminance = color_utils::GetLuminanceForColor(style->background_color);
-  style->text_color = (luminance >= kDarkTextLuminanceThreshold ?
-      kDefaultTextColorDark : kDefaultTextColorLight);
+  const uint8_t luma = color_utils::Luma(style->background_color);
+  style->text_color = (luma >= kDarkTextLumaThreshold) ?
+      kDefaultTextColorDark : kDefaultTextColorLight;
 }
 
 bool ValidateFallbackIconStyle(const FallbackIconStyle& style) {
@@ -64,20 +64,20 @@ bool ValidateFallbackIconStyle(const FallbackIconStyle& style) {
 void SetDominantColorAsBackground(
     const scoped_refptr<base::RefCountedMemory>& bitmap_data,
     FallbackIconStyle* style) {
-  // Try to ensure color's luminance isn't too large so that light text is
+  // Try to ensure color's lightness isn't too large so that light text is
   // visible. Set an upper bound for the dominant color.
-  const color_utils::HSL lower_bound{-1.0, -1.0, kMinBackgroundColorLuminance};
-  const color_utils::HSL upper_bound{-1.0, -1.0, kMaxBackgroundColorLuminance};
+  const color_utils::HSL lower_bound{-1.0, -1.0, kMinBackgroundColorLightness};
+  const color_utils::HSL upper_bound{-1.0, -1.0, kMaxBackgroundColorLightness};
   color_utils::GridSampler sampler;
   SkColor dominant_color = color_utils::CalculateKMeanColorOfPNG(
       bitmap_data, lower_bound, upper_bound, &sampler);
   // |CalculateKMeanColorOfPNG| will try to return a color that lies within the
   // specified bounds if one exists in the image. If there's no such color, it
   // will return the dominant color which may be lighter than our upper bound.
-  // Clamp luminance down to a reasonable maximum value so text is readable.
+  // Clamp lightness down to a reasonable maximum value so text is readable.
   color_utils::HSL color_hsl;
   color_utils::SkColorToHSL(dominant_color, &color_hsl);
-  color_hsl.l = std::min(color_hsl.l, kMaxBackgroundColorLuminance);
+  color_hsl.l = std::min(color_hsl.l, kMaxBackgroundColorLightness);
   style->background_color =
       color_utils::HSLToSkColor(color_hsl, SK_AlphaOPAQUE);
 }