@NonNull
    CustomTabColorSchemeParams withDefaults(@NonNull CustomTabColorSchemeParams defaults) {
        return new CustomTabColorSchemeParams(
                toolbarColor == null ? defaults.toolbarColor : toolbarColor,
                secondaryToolbarColor == null ? defaults.secondaryToolbarColor
                        : secondaryToolbarColor,
                navigationBarColor == null ? defaults.navigationBarColor : navigationBarColor);
    }
Replaces the null fields with values from provided defaults.
customtabs/src/android/support/customtabs/CustomTabColorSchemeParams.java