module Sprockets::Processing

end
data.gsub(...)
register_preprocessor :my_processor do |context, data|

A block can be passed for to create a shorthand processor.

register_preprocessor 'text/css', Sprockets::DirectiveProcessor

Registers a new Preprocessor `klass` for `mime_type`.

def register_preprocessor(mime_type, klass, &block)
  expire_index!
  if block_given?
    name  = klass.to_s
    klass = Class.new(Processor) do
      @name      = name
      @processor = block
    end
  end
  @preprocessors[mime_type].push(klass)
end