# File lib/selenium/webdriver/common/html5/shared_web_storage.rb, line 14
        def fetch(key, &blk)
          if self.key? key
            return self[key]
          end

          if block_given?
            yield key
          else
            # should be KeyError, but it's 1.9-specific
            raise IndexError, "missing key #{key.inspect}" 
          end
        end