Macro rocket_include_handlebars::handlebars_response_cache

macro_rules! handlebars_response_cache {
    ($cm:expr, $etag_if_none_match:expr, $key:expr, $gen:block) => { ... };
}

Used for wrapping a HandlebarsResponse and its constructor, and use a key to cache its HTML and ETag in memory. The cache is generated only when you are using the release profile.