Void displayPage(Void() fn, [Pair<String, String> ] headers)
fn: A Void function taking no parameters that prints the content to standard output.
headers: A list of key-value pairs of HTTP headers
Displays a function result. The displayPage functions are called
automatically by a webapp based on the return value of
webmain and should only be called directly for debugging
purposes and when constructing custom
This function may be useful for output of very large amounts of content where reading the entire content into a string or binary block before printing it is not practical.