module Sprockets::Rails::Helper

def lookup_debug_asset(path, options = {})

eventually be removed w/ Sprockets 3.x.
Internal method to support multifile debugging. Will 
def lookup_debug_asset(path, options = {})
  path = path_with_extname(path, options)
  resolve_asset do |resolver|
    resolver.find_debug_asset path
  end
end