Don't fall back to default incognito colors and tints when using a custom theme.

chrome/browser/themes/theme_service.cc

Index: chrome/browser/themes/theme_service.cc
diff --git a/chrome/browser/themes/theme_service.cc b/chrome/browser/themes/theme_service.cc
index be26a3022714599167053cffd81c756114735bb1..659d013623b37418e1ffeeab0abecd3ef4fc1a2d 100644
--- a/chrome/browser/themes/theme_service.cc
+++ b/chrome/browser/themes/theme_service.cc
@@ -346,7 +346,9 @@ color_utils::HSL ThemeService::GetTint(int id, bool incognito) const {
   if (theme_supplier_ && theme_supplier_->GetTint(id, &hsl))
     return hsl;
 
-  return ThemeProperties::GetDefaultTint(id, incognito);
+  // Always fall back to the non-incognito tint when there's a custom theme.
+  // See comment in GetDefaultColor().
+  return ThemeProperties::GetDefaultTint(id, incognito && !theme_supplier_);
 }
 
 void ThemeService::ClearAllThemeData() {
@@ -622,7 +624,10 @@ SkColor ThemeService::GetColor(int id, bool incognito) const {
     }
   }
 
-  return ThemeProperties::GetDefaultColor(id, incognito);
+  // Always fall back to the non-incognito color when there's a custom theme
+  // because the default (classic) incognito color may be dramatically different
+  // (optimized for a light-on-dark color).
+  return ThemeProperties::GetDefaultColor(id, incognito && !theme_supplier_);
 }
 
 int ThemeService::GetDisplayProperty(int id) const {