Replace Manage Languages with dialog and dropdown item

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 57 matching lines @@
       iron-dropdown .dropdown-item:focus,
       paper-dropdown-menu .dropdown-item:focus {
         @apply(--cr-selectable-focus);
       }
 
       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 .dropdown-item:not([disabled]),
       iron-dropdown .dropdown-content paper-item {
         @apply(--settings-actionable);
       }
 
+      iron-dropdown .dropdown-content .dropdown-item[disabled] {
+        opacity: .65;
+      }
+
       span ~ a {
         -webkit-margin-start: 4px;
       }
 
       [is='action-link'],
       [is='action-link']:active,
       [is='action-link']:hover,
       [is='action-link']:visited,
       .primary-button,
       .tertiary-button {
@@ skipping 125 matching lines @@
         flex: 1;
         margin: 8px 16px;
       }
 
       /* The start (left in LTR) part (horizontally) of a list item. */
       .list-item > .start {
         flex: 1;
       }
 
       .list-item > label span[disabled] {
-        opacity: .65;  /* TODO(michaelpg): check this value with bettes. */
+        opacity: .65;
       }
 
       .list-item > paper-icon-item {
         padding: 0;
       }
 
       /* This button has no ink ripple. */
       .list-item.list-button {
         align-items: center;
         color: var(--google-blue-500);
@@ skipping 123 matching lines @@
         content: '';
         height: 10px;
         position: absolute;
         right: -5px;
         top: 10px;
         width: 10px;
       }
     </style>
   </template>
 </dom-module>