function mixSpecIntoComponent(Constructor, spec) {
  if (!spec) {
    return;
  }

  !(typeof spec !== 'function') ? "development" !== 'production' ? invariant(false, 'ReactClass: You\'re attempting to ' + 'use a component class as a mixin. Instead, just use a regular object.') : invariant(false) : undefined;
  !!ReactElement.isValidElement(spec) ? "development" !== 'production' ? invariant(false, 'ReactClass: You\'re attempting to ' + 'use a component as a mixin. Instead, just use a regular object.') : invariant(false) : undefined;

  var proto = Constructor.prototype;

  // By handling mixins before any other properties, we ensure the same
  // chaining order is applied to methods with DEFINE_MANY policy, whether
  // mixins are listed before or after these methods in the spec.
  if (spec.hasOwnProperty(MIXINS_KEY)) {
    RESERVED_SPEC_KEYS.mixins(Constructor, spec.mixins);
  }

  for (var name in spec) {
    if (!spec.hasOwnProperty(name)) {
      continue;
    }

    if (name === MIXINS_KEY) {
      // We have already handled mixins in a special case above.
      continue;
    }

    var property = spec[name];
    validateMethodOverride(proto, name);

    if (RESERVED_SPEC_KEYS.hasOwnProperty(name)) {
      RESERVED_SPEC_KEYS[name](Constructor, property);
    } else {
      // Setup methods on prototype:
      // The following member methods should not be automatically bound:
      // 1. Expected ReactClass methods (in the "interface").
      // 2. Overridden methods (that were mixed in).
      var isReactClassMethod = ReactClassInterface.hasOwnProperty(name);
      var isAlreadyDefined = proto.hasOwnProperty(name);
      var isFunction = typeof property === 'function';
      var shouldAutoBind = isFunction && !isReactClassMethod && !isAlreadyDefined && spec.autobind !== false;

      if (shouldAutoBind) {
        if (!proto.__reactAutoBindMap) {
          proto.__reactAutoBindMap = {};
        }
        proto.__reactAutoBindMap[name] = property;
        proto[name] = property;
      } else {
        if (isAlreadyDefined) {
          var specPolicy = ReactClassInterface[name];

          // These cases should already be caught by validateMethodOverride.
          !(isReactClassMethod && (specPolicy === SpecPolicy.DEFINE_MANY_MERGED || specPolicy === SpecPolicy.DEFINE_MANY)) ? "development" !== 'production' ? invariant(false, 'ReactClass: Unexpected spec policy %s for key %s ' + 'when mixing in component specs.', specPolicy, name) : invariant(false) : undefined;

          // For methods which are defined more than once, call the existing
          // methods before calling the new property, merging if appropriate.
          if (specPolicy === SpecPolicy.DEFINE_MANY_MERGED) {
            proto[name] = createMergedResultFunction(proto[name], property);
          } else if (specPolicy === SpecPolicy.DEFINE_MANY) {
            proto[name] = createChainedFunction(proto[name], property);
          }
        } else {
          proto[name] = property;
          if ("development" !== 'production') {
            // Add verbose displayName to the function, which helps when looking
            // at profiling tools.
            if (typeof property === 'function' && spec.displayName) {
              proto[name].displayName = spec.displayName + '_' + name;
            }
          }
        }
      }
    }
  }
}
Mixin helper which handles policy validation and reserved
specification keys when building React classses.