color_utils cleanup:

ash/frame/default_header_painter.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 "ash/frame/default_header_painter.h"
 
 #include "ash/ash_layout_constants.h"
 #include "ash/frame/caption_buttons/frame_caption_button_container_view.h"
 #include "ash/frame/header_painter_util.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 24 matching lines @@
 const SkColor kTitleTextColor = SkColorSetRGB(40, 40, 40);
 // Color of the active window header/content separator line.
 const SkColor kHeaderContentSeparatorColor = SkColorSetRGB(150, 150, 152);
 // Color of the inactive window header/content separator line.
 const SkColor kHeaderContentSeparatorInactiveColor =
     SkColorSetRGB(180, 180, 182);
 // The default color of the frame.
 const SkColor kDefaultFrameColor = SkColorSetRGB(242, 242, 242);
 // Duration of crossfade animation for activating and deactivating frame.
 const int kActivationCrossfadeDurationMs = 200;
-// Luminance below which to use white caption buttons.
-const int kMaxLuminanceForLightButtons = 125;
 
 // Tiles an image into an area, rounding the top corners.
 void TileRoundRect(gfx::Canvas* canvas,
                    const SkPaint& paint,
                    const gfx::Rect& bounds,
                    int corner_radius) {
   SkRect rect = gfx::RectToSkRect(bounds);
   const SkScalar corner_radius_scalar = SkIntToScalar(corner_radius);
   SkScalar radii[8] = {
       corner_radius_scalar, corner_radius_scalar,  // top-left
@@ skipping 215 matching lines @@
   gfx::ScopedCanvas scoped_canvas(canvas);
   const float scale = canvas->UndoDeviceScaleFactor();
   gfx::RectF rect(0, painted_height_ * scale - 1, view_->width() * scale, 1);
   SkPaint paint;
   paint.setColor((mode_ == MODE_ACTIVE) ?
       kHeaderContentSeparatorColor : kHeaderContentSeparatorInactiveColor);
   canvas->sk_canvas()->drawRect(gfx::RectFToSkRect(rect), paint);
 }
 
 bool DefaultHeaderPainter::ShouldUseLightImages() {
-  int luminance = color_utils::GetLuminanceForColor(
-      mode_ == MODE_INACTIVE ? inactive_frame_color_ : active_frame_color_);
-  return luminance < kMaxLuminanceForLightButtons;
+  return color_utils::IsDark(mode_ == MODE_INACTIVE ? inactive_frame_color_

[Peter Kasting, 2016/03/04 01:39:26]

This is not quite the same as the old code, but almost; it's basically "< 128"
instead of "< 125".  This difference is so small I have a hard time believing it
matters; using the standard function seems better.

+                                                    : active_frame_color_);
 }
 
 void DefaultHeaderPainter::UpdateAllButtonImages() {
   caption_button_container_->SetUseLightImages(ShouldUseLightImages());
   caption_button_container_->SetButtonImage(
       CAPTION_BUTTON_ICON_MINIMIZE, gfx::VectorIconId::WINDOW_CONTROL_MINIMIZE);
 
   UpdateSizeButtonImages();
 
   caption_button_container_->SetButtonImage(
@@ skipping 24 matching lines @@
   return HeaderPainterUtil::GetTitleBounds(
       left_header_view_, caption_button_container_, GetTitleFontList());
 }
 
 bool DefaultHeaderPainter::UsesCustomFrameColors() const {
   return active_frame_color_ != kDefaultFrameColor ||
          inactive_frame_color_ != kDefaultFrameColor;
 }
 
 }  // namespace ash