[cocoa] increase tab strip contrast in "Increase Contrast" mode

chrome/browser/ui/cocoa/tabs/tab_strip_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.
 
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_view.h"
 
 #include <cmath>  // floor
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
@@ skipping 65 matching lines @@
       BOOL focused = [window isMainWindow];
       NSDrawThreePartImage(borderRect, nil, image, nil, /*vertical=*/ NO,
                            NSCompositeSourceOver,
                            focused ?  1.0 : tabs::kImageNoFocusAlpha,
                            /*flipped=*/ NO);
     }
 
     return;
   }
 
+  NSColor* strokeColor;
   if (themeProvider->HasCustomImage(IDR_THEME_TOOLBAR) ||
       themeProvider->HasCustomColor(ThemeProperties::COLOR_TOOLBAR)) {
     // First draw the toolbar bitmap, so that theme colors can shine through.
     NSRect backgroundRect = [self bounds];
     backgroundRect.size.height = [self cr_lineWidth];
     if (NSIntersectsRect(backgroundRect, dirtyRect)) {
       [self drawBackground:backgroundRect];
     }
 
     // Pre-MD the IDR_TOOLBAR_SHADE_TOP image would lay down a light highlight
     // which helped dark toolbars stand out from dark frames. Lay down a thin
     // highlight in MD also.
     if ([window isMainWindow]) {
-      [themeProvider->GetNSColor(
-          ThemeProperties::COLOR_TOOLBAR_STROKE_THEME) set];
+      strokeColor = themeProvider->GetNSColor(
+          ThemeProperties::COLOR_TOOLBAR_STROKE_THEME);
     } else {
-      [themeProvider->GetNSColor(
-          ThemeProperties::COLOR_TOOLBAR_STROKE_THEME_INACTIVE) set];
+      strokeColor = themeProvider->GetNSColor(
+          ThemeProperties::COLOR_TOOLBAR_STROKE_THEME_INACTIVE);
     }
   } else {
-    [themeProvider->GetNSColor(ThemeProperties::COLOR_TOOLBAR_STROKE) set];
+    strokeColor =
+        themeProvider->GetNSColor(ThemeProperties::COLOR_TOOLBAR_STROKE);
   }
+
+  if (themeProvider->ShouldIncreaseContrast())
+    strokeColor = [strokeColor colorWithAlphaComponent:100];
+  [strokeColor set];
+
   NSRect borderRect = NSMakeRect(0.0, 0.0, self.bounds.size.width,
       [self cr_lineWidth]);
   NSRectFillUsingOperation(NSIntersectionRect(dirtyRect, borderRect),
                            NSCompositeSourceOver);
 }
 
 - (void)drawRect:(NSRect)dirtyRect {
   const ui::ThemeProvider* themeProvider = [[self window] themeProvider];
   bool hasCustomThemeImage = themeProvider &&
       themeProvider->HasCustomImage(IDR_THEME_FRAME);
@@ skipping 300 matching lines @@
   } else {
     [visualEffectView setState:NSVisualEffectStateFollowsWindowActiveState];
   }
 }
 
 - (void)windowDidChangeActive {
   [self setNeedsDisplay:YES];
 }
 
 @end