MD WebUI: Move some settings CSS to shared_style_css

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_root_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;
         font-size: 100%;
         font-weight: 500;
@@ skipping 45 matching lines @@
         text-align: start;
         width: 100%;
       }
 
       paper-dropdown-menu .dropdown-item.iron-selected {
         font-weight: bold;
       }
 
       iron-dropdown .dropdown-item:focus,
       paper-dropdown-menu .dropdown-item:focus {
-        background-color: var(--paper-grey-300);
+        background-color: var(--cr-focused-item-color);
         outline: none;
       }
 
       iron-dropdown .dropdown-content {
         background-color: white;
         box-shadow: 0 2px 6px var(--paper-grey-500);
       }
 
       iron-dropdown .dropdown-content .dropdown-item,
       iron-dropdown .dropdown-content paper-item {
@@ skipping 194 matching lines @@
         display: block;
       }
 
       /*
        * A row with two lines of text. Often the lower line will be .secondary.
        */
       .settings-box.two-line {
         min-height: 56px;
       }
 
-      [actionable] {
-        @apply(--settings-actionable);
-      }
-
       /* The lower line of text in a .settings-box.two-line. */
       .settings-box .secondary {
         @apply(--settings-secondary);
       }
 
       /* The middle part (horizontally) of a row. */
       .settings-box .middle {
         -webkit-margin-start: 16px;
         align-items: center;
         flex: auto;
@@ skipping 46 matching lines @@
 
       .favicon-image {
         background-repeat: no-repeat;
         background-size: contain;
         height: 16px;
         width: 16px;
       }
     </style>
   </template>
 </dom-module>