simplify children updates

src/core/instance/lifecycle.js

@@ -81,9 +81,8 @@ export function lifecycleMixin (Vue) {
     }
   }
 
-  Vue.prototype._updateFromParent = function (propsData, listeners, parentVnode, children) {
+  Vue.prototype._updateFromParent = function (propsData, listeners, parentVnode) {
     this.$options._parentVnode = parentVnode
-    this.$options._renderChildren = children
     // update props
     if (propsData && this.$options.props) {
       observerState.shouldConvert = false

src/core/instance/render.js

@@ -89,9 +89,9 @@ export function renderMixin (Vue) {
   }
 }
 
-function resolveSlots (vm, children) {
-  if (children) {
-    children = flatten(isArray(children) ? children : children())
+function resolveSlots (vm, renderChildren) {
+  if (renderChildren) {
+    const children = flatten(renderChildren())
     const slots = { default: children }
     let i = children.length
     let name, child

src/core/vdom/create-component.js

@@ -83,13 +83,12 @@ function init (vnode) {
 }
 
 function prepatch (oldVnode, vnode) {
-  const { listeners, propsData, children } = vnode.componentOptions
+  const { listeners, propsData } = vnode.componentOptions
   vnode.child = oldVnode.child
   vnode.child._updateFromParent(
     propsData, // updated props
     listeners, // updated listeners
-    vnode, // new parent vnode
-    children // new children
+    vnode // new parent vnode
   )
 }