code: public static StopwatchSource<HttpServletRequest> newCacheStopwatchSource(StopwatchSource<HttpServletRequest> stopwatchSource) {
  		return new CachedStopwatchSource<HttpServletRequest, String>(stopwatchSource) {
  			@Override
  			protected String getLocationKey(HttpServletRequest location) {
  				return location.getRequestURI();
  			}
  		};
  	}
docs: Wraps given stop watch source in a cache.
  
  @param stopwatchSource Stopwatch source
  @return Cached stopwatch source