[MD settings] replace secondary-action with separator

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">
       :host-context([dir=rtl]) button[is='paper-icon-button-light'] {
         transform: scaleX(-1);  /* Flip on the X axis (aka mirror). */
       }
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         align-items: center;
         flex: auto;
       }
 
       .no-outline,
       [scrollable] .no-outline {
         background: none;
         outline: none;
       }
 
-      /* TODO(dschuyler): replace with .separator.
-       * The secondary-action wraps a clickable sub-area of a .settings-box.
-       * Here is an example with and without a secondary action box:
-       *
-       *  +-------------------------------------------------------+
-       *  | Main action area .settings-box    | .secondary-action |
-       *  +-------------------------------------------------------+
-       *  | Another setting-box without a secondary-action        |
-       *  +-------------------------------------------------------+ */
-      :-webkit-any(.settings-box, .list-item) .secondary-action {
-        -webkit-border-start: var(--settings-separator-line);
-        -webkit-margin-start: 20px;
-        -webkit-padding-start: 20px;
-        align-items: center;
-        display: flex;
-        flex-shrink: 0;
-        height: 36px;
-      }
-
-      :-webkit-any(.settings-box, .list-item).two-line .secondary-action {
-        height: 46px;
-      }
-
       /* Helper for a list frame to automatically avoid the separator line. */
       .vertical-list > *:not(:first-of-type) {
         border-top: var(--settings-separator-line);
       }
 
       /* The separator a vertical line like a horizontal rule <hr> tag, but goes
        * the other way. An example is near the |sign out| button on the People
        * settings. */
       :-webkit-any(.settings-box, .list-item) .separator {
         -webkit-border-start: var(--settings-separator-line);
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         transform: rotate(-135deg);
       }
 
       .column-header {
         color: var(--paper-grey-600);
         font-weight: 500;
       }
     </style>
   </template>
 </dom-module>