cocoa: darken toolbar buttons in Increase Contrast mode

chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.mm

 // Copyright (c) 2011 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.
 
 #import "chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "chrome/app/vector_icons/vector_icons.h"
 #import "chrome/browser/ui/cocoa/image_button_cell.h"
@@ skipping 206 matching lines @@
     case VIEW_ID_APP_MENU:
       return &kBrowserToolsIcon;
     default:
       break;
   }
 
   return nullptr;
 }
 
 - (SkColor)vectorIconColor:(BOOL)themeIsDark {
-  return themeIsDark ? SK_ColorWHITE : SkColorSetRGB(0x5A, 0x5A, 0x5A);
+  const ui::ThemeProvider* provider = [[self window] themeProvider];
+  return themeIsDark ? SK_ColorWHITE
+                     : (provider && provider->ShouldIncreaseContrast()
+                            ? SK_ColorBLACK
+                            : SkColorSetRGB(0x5A, 0x5A, 0x5A));
 }
 
 - (NSImage*)browserToolsIconForFillColor:(SkColor)fillColor {
   // Create a |BrowserToolsImageRep| to draw the browser tools icon using
   // the provided fill color.
   base::scoped_nsobject<BrowserToolsImageRep> imageRep(
       [[BrowserToolsImageRep alloc]
           initWithDrawSelector:@selector(drawBrowserToolsIcon:)
                       delegate:[BrowserToolsImageRep class]]);
   [imageRep setFillColor:skia::SkColorToSRGBNSColor(fillColor)];
@@ skipping 143 matching lines @@
 
 - (void)windowDidChangeTheme {
   // Update the hover and pressed image backgrounds to match the current theme.
   [self resetButtonStateImages];
 }
 
 - (void)windowDidChangeActive {
 }
 
 @end