allow router-views to take named slots

Author: yyx990803

src/components/view.js

@@ -9,9 +9,12 @@ export default {
       default: 'default'
     }
   },
-  render (h, { props, children, parent, data }) {
+  render (_, { props, children, parent, data }) {
     data.routerView = true
 
+    // directly use parent context's createElement() function
+    // so that components rendered by router-view can resolve named slots
+    const h = parent.$createElement
     const name = props.name
     const route = parent.$route
     const cache = parent._routerViewCache || (parent._routerViewCache = {})