Scroll: feat scroll always show

packages/scrollbar/src/main.js

@@ -93,7 +93,7 @@ export default {
         </div>
       ]);
     }
-    return h('div', { class: 'el-scrollbar' }, nodes);
+    return h('div', { 'class': ['el-scrollbar', this.always ? 'is-always' : ''] }, nodes);
   },
 
   methods: {

packages/theme-chalk/src/scrollbar.scss

@@ -14,6 +14,12 @@
     }
   }
 
+  @include when(always){
+    @include e(bar) {
+      opacity: 1;
+    }
+  }
+
   @include e(wrap) {
     overflow: scroll;
     height: 100%;