cocoa: draw BackgroundGradientView separators darker in Increase Contrast mode

chrome/browser/ui/cocoa/background_gradient_view.mm

 // Copyright (c) 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/cocoa/background_gradient_view.h"
 
 #import "chrome/browser/themes/theme_properties.h"
 #import "chrome/browser/themes/theme_service.h"
 #import "chrome/browser/ui/cocoa/themed_window.h"
 #include "chrome/grit/theme_resources.h"
@@ skipping 80 matching lines @@
   // active (e.g, OmniboxPopupTopSeparatorView). For these, check the status
   // of parentWindow instead. Note that this is not tracked correctly (but
   // the views that do this appear to be removed when the window loses focus
   // anyway).
   if ([window parentWindow])
     window = [window parentWindow];
 
   const ui::ThemeProvider* themeProvider = [window themeProvider];
   if (!themeProvider)
     return [NSColor blackColor];
+  if (themeProvider->ShouldIncreaseContrast()) {
+    if ([window hasDarkTheme])
+      return [NSColor whiteColor];
+    else
+      return [NSColor blackColor];
+  }
   return themeProvider->GetNSColor(
              ThemeProperties::COLOR_DETACHED_BOOKMARK_BAR_SEPARATOR);
 }
 
 - (NSColor*)backgroundImageColor {
   const ui::ThemeProvider* themeProvider = [[self window] themeProvider];
   if (!themeProvider)
     return [[self window] backgroundColor];
 
   // Themes don't have an inactive image so only look for one if there's no
@@ skipping 62 matching lines @@
 
 - (void)windowDidChangeTheme {
   [self setNeedsDisplay:YES];
 }
 
 - (void)windowDidChangeActive {
   [self setNeedsDisplay:YES];
 }
 
 @end