Settings/Oobe: Simplify cr-network-select and use flex

ui/webui/resources/cr_elements/network/cr_network_list.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_scrollable_behavior.html">
 <link rel="import" href="chrome://resources/cr_elements/network/cr_network_list_item.html">
 <link rel="import" href="chrome://resources/cr_elements/network/cr_onc_types.html">
 
 <dom-module id="cr-network-list">
   <template>
     <style include="cr-shared-style">
+      :host {
+        display: inline-flex;
+      }
       #container {
         max-height: 1000px;
         min-height: 50px;
         overflow-y: auto;
       }
     </style>
-    <div id="container" class="layout vertical" scrollable>
+    <div id="container" class="layout vertical flex" scrollable>
       <iron-list items="[[getItems_(networks, customItems)]]"
           scroll-target="container" selection-enabled
           selected-item="{{selectedItem}}">
         <template>
           <cr-network-list-item item="[[item]]" is-list-item
               show-buttons="[[showButtons]]" tabindex$="[[tabIndex]]">
           </cr-network-list-item>
         </template>
       </iron-list>
     </div>
   </template>
   <script src="cr_network_list.js"></script>
 </dom-module>