docs: function mergeVNodeHook (def, hookKey, hook, key) {
  	  key = key + hookKey;
  	  var injectedHash = def.__injected || (def.__injected = {});
  	  if (!injectedHash[key]) {
  	    injectedHash[key] = true;
  	    var oldHook = def[hookKey];
  	    if (oldHook) {
  	      def[hookKey] = function () {
  	        oldHook.apply(this, arguments);
  	        hook.apply(this, arguments);
  	      };
  	    } else {
  	      def[hookKey] = hook;
  	    }
  	  }
  	}