MD Settings: Introduce CrScrollableBehavior

chrome/browser/resources/settings/settings_shared_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="/settings_vars_css.html">
 
 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style include="cr-shared-style">
       h2 {
         align-items: center;
         display: flex;
@@ skipping 163 matching lines @@
       }
 
       .button-strip {
         text-align: end;
       }
 
       /* A list-frame is an outer container for list-items. It is intended to be
        * outside of a settings-box. A list-frame is likely to follow a
        * settings box. */
       .list-frame {
-        -webkit-padding-end: 20px;
-        -webkit-padding-start: 56px;
+        @apply(--settings-list-frame-padding);
         align-items: center;
         display: block;
-        padding-bottom: 0;
-        padding-top: 0;
       }
 
       .list-frame .secondary,
       .list-item .secondary {
         @apply(--settings-secondary);
       }
 
       /* A list-item is intended to be contained within a list-frame. The list
        * frame will setup the initial start margin. */
       .list-item {
@@ skipping 164 matching lines @@
         content: '';
         height: 10px;
         position: absolute;
         right: -5px;
         top: 10px;
         width: 10px;
       }
     </style>
   </template>
 </dom-module>