docs: function continuer(verb, arg) {
              var result;
  
              // Until V8 3.19 / Chromium 29 is released, SpiderMonkey is the only
              // engine that has a deployed base of browsers that support generators.
              // However, SM's generators use the Python-inspired semantics of
              // outdated ES6 drafts.  We would like to support ES6, but we'd also
              // like to make it possible to use generators in deployed browsers, so
              // we also support Python-style generators.  At some point we can remove
              // this block.
  
              if (typeof StopIteration === "undefined") {
                  // ES6 Generators
                  try {
                      result = generator[verb](arg);
                  } catch (exception) {
                      return reject(exception);
                  }
                  if (result.done) {
                      return Q(result.value);
                  } else {
                      return when(result.value, callback, errback);
                  }
              } else {
                  // SpiderMonkey Generators
                  // FIXME: Remove this case when SM does ES6 generators.
                  try {
                      result = generator[verb](arg);
                  } catch (exception) {
                      if (isStopIteration(exception)) {
                          return Q(exception.value);
                      } else {
                          return reject(exception);
                      }
                  }
                  return when(result, callback, errback);
              }
          }