MD Settings: Use scrollable behavior for all iron-list containers

ui/webui/resources/cr_elements/shared_style_css.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/shared_vars_css.html">
 
 <!-- Common styles for Material Design WebUI. Included directly in
   settings_shared_css.html. -->
 <dom-module id="cr-shared-style">
   <template>
     <style>
       /* Chrome spinners should be blue. */
       paper-spinner {
@@ skipping 43 matching lines @@
         border-bottom-color: var(--google-grey-300);
       }
       [scrollable] :focus {
         @apply(--cr-list-item-focus);
         @apply(--cr-selectable-focus);
       }
       [scrollable] iron-list > * {
         @apply(--cr-actionable);
       }
 
+      .scroll-container {
+        display: flex;
+        flex-direction: column;
+        min-height: 1px;
+      }
+
       [selectable]:focus,
       [selectable] > :focus {
         @apply(--cr-selectable-focus);
       }
       [selectable] > * {
         @apply(--cr-actionable);
       }
     </style>
   </template>
 </dom-module>