[Mac][Material Design] Adjust tabstrip Incognito, non-vibrant bg color.

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 114 matching lines @@
   // somewhat opaque for Incognito mode, very opaque for non-Incognito mode, and
   // completely opaque when the window is not active.
   if (themeProvider && !hasCustomThemeImage && isModeMaterial &&
       !inATabDraggingOverlayWindow_) {
     NSColor* theColor = nil;
     if (isMainWindow) {
       if (supportsVibrancy &&
           !themeProvider->HasCustomColor(ThemeProperties::COLOR_FRAME)) {
         theColor = themeProvider->GetNSColor(
             ThemeProperties::COLOR_FRAME_VIBRANCY_OVERLAY);
+      } else if (!supportsVibrancy && themeProvider->InIncognitoMode()) {
+        theColor = [NSColor colorWithSRGBRed:20 / 255.
+                                       green:22 / 255.
+                                        blue:24 / 255.
+                                       alpha:1];
       } else {
         theColor = themeProvider->GetNSColor(ThemeProperties::COLOR_FRAME);
       }
     } else {
       theColor = themeProvider->GetNSColor(
           ThemeProperties::COLOR_FRAME_INACTIVE);
     }
 
     if (theColor) {
       [theColor set];
@@ skipping 268 matching lines @@
   } else {
     [visualEffectView setState:NSVisualEffectStateFollowsWindowActiveState];
   }
 }
 
 - (void)windowDidChangeActive {
   [self setNeedsDisplay:YES];
 }
 
 @end