color_utils cleanup:

apps/ui/views/app_window_frame_view.cc

 // Copyright 2014 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 "apps/ui/views/app_window_frame_view.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "extensions/browser/app_window/native_app_window.h"
 #include "extensions/common/draggable_region.h"
 #include "grit/theme_resources.h"
@@ skipping 356 matching lines @@
 
 SkColor AppWindowFrameView::CurrentFrameColor() {
   return widget_->IsActive() ? active_frame_color_ : inactive_frame_color_;
 }
 
 void AppWindowFrameView::SetButtonImagesForFrame() {
   DCHECK(draw_frame_);
 
   // If the frame is dark, we should use the light images so they have
   // some contrast.
-  unsigned char frame_luma =
-      color_utils::GetLuminanceForColor(CurrentFrameColor());
-  const unsigned char kLuminanceThreshold = 100;
-  bool use_light = frame_luma < kLuminanceThreshold;
+  const uint8_t kLumaThreshold = 100;
+  bool use_light = color_utils::Luma(CurrentFrameColor()) < kLumaThreshold;
 
   ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
   if (use_light) {
     maximize_button_->SetImage(
         views::CustomButton::STATE_NORMAL,
         rb.GetNativeImageNamed(IDR_APP_WINDOW_MAXIMIZE_L).ToImageSkia());
     restore_button_->SetImage(
         views::CustomButton::STATE_NORMAL,
         rb.GetNativeImageNamed(IDR_APP_WINDOW_RESTORE_L).ToImageSkia());
     minimize_button_->SetImage(
         views::CustomButton::STATE_NORMAL,
         rb.GetNativeImageNamed(IDR_APP_WINDOW_MINIMIZE_L).ToImageSkia());
   } else {
     maximize_button_->SetImage(
         views::CustomButton::STATE_NORMAL,
         rb.GetNativeImageNamed(IDR_APP_WINDOW_MAXIMIZE).ToImageSkia());
     restore_button_->SetImage(
         views::CustomButton::STATE_NORMAL,
         rb.GetNativeImageNamed(IDR_APP_WINDOW_RESTORE).ToImageSkia());
     minimize_button_->SetImage(
         views::CustomButton::STATE_NORMAL,
         rb.GetNativeImageNamed(IDR_APP_WINDOW_MINIMIZE).ToImageSkia());
   }
 }
 
 }  // namespace apps