Try to improve toolbar separator coloration for themed browser windows.

chrome/browser/ui/views/frame/browser_view.cc

 // Copyright 2012 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 "chrome/browser/ui/views/frame/browser_view.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 203 matching lines @@
   // In detached mode, the bar is meant to overlap with |contents_container_|.
   // The detached background color may be partially transparent, but the layer
   // for |view| must be painted opaquely to avoid subpixel anti-aliasing
   // artifacts, so we recreate the contents container base color here.
   canvas->FillRect(fill_rect,
                    tp->GetColor(ThemeProperties::COLOR_CONTROL_BACKGROUND));
   canvas->FillRect(
       fill_rect,
       tp->GetColor(ThemeProperties::COLOR_DETACHED_BOOKMARK_BAR_BACKGROUND));
 
-  // Draw the separators above and below bookmark bar;
-  // if animating, these are fading in/out.
-  SkColor separator_color =
-      tp->GetColor(ThemeProperties::COLOR_DETACHED_BOOKMARK_BAR_SEPARATOR);

[Evan Stade, 2017/01/13 01:16:52]

This code looks weird because when the code was originally written, it drew a
separator at the top as well (where the luma wasn't touched). As part of MD,
that was changed to be drawn by the toolbar instead. Now there are two separate
color identifiers so the calculation can be done in ThemeService.

-
-  // For the bottom separator, increase the luminance. Either double it or halve
-  // the distance to 1.0, whichever is less of a difference.
-  color_utils::HSL hsl;
-  color_utils::SkColorToHSL(separator_color, &hsl);
-  hsl.l = std::min((hsl.l + 1) / 2, hsl.l * 2);
+  // Draw the separator below the detached bookmark bar.
   BrowserView::Paint1pxHorizontalLine(
-      canvas, color_utils::HSLToSkColor(hsl, SK_AlphaOPAQUE),
+      canvas,
+      tp->GetColor(ThemeProperties::COLOR_DETACHED_BOOKMARK_BAR_SEPARATOR),
       view->GetLocalBounds(), true);
 }
 
 // Paints the background (including the theme image behind content area) for
 // the Bookmarks Bar when it is attached to the Toolbar into |bounds|.
 // |background_origin| is the origin to use for painting the theme image.
 void PaintBackgroundAttachedMode(gfx::Canvas* canvas,
                                  const ui::ThemeProvider* theme_provider,
                                  const gfx::Rect& bounds,
                                  const gfx::Point& background_origin) {
@@ skipping 2398 matching lines @@
 }
 
 extensions::ActiveTabPermissionGranter*
 BrowserView::GetActiveTabPermissionGranter() {
   content::WebContents* web_contents = GetActiveWebContents();
   if (!web_contents)
     return nullptr;
   return extensions::TabHelper::FromWebContents(web_contents)
       ->active_tab_permission_granter();
 }