@Override
        public boolean validateRelationship(
                ICustomTabsCallback callback, @Relation int relation, Uri origin, Bundle extras) {
            return CustomTabsService.this.validateRelationship(
                    new CustomTabsSessionToken(callback, getSessionIdFromBundle(extras)),
                    relation, origin, extras);
        }
File is a splash image to be shown on top of a Trusted Web Activity while the web contents
are loading.
customtabs/src/android/support/customtabs/CustomTabsService.java