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

chrome/browser/ui/cocoa/tabs/tab_strip_view.mm

Index: chrome/browser/ui/cocoa/tabs/tab_strip_view.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_strip_view.mm b/chrome/browser/ui/cocoa/tabs/tab_strip_view.mm
index e242b32a65215beb5c03af6ecd65607fad30f908..8334d31dd830815a074bd3be78df351dac30b8f8 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_strip_view.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_strip_view.mm
@@ -132,6 +132,11 @@
           !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);
       }