MD Settings: Replace paper-item with button under iron-dropdown, part1.

chrome/browser/resources/settings/certificate_manager_page/certificate_subentry.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-dropdown/iron-dropdown.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="/certificate_manager_page/certificate_manager_types.html">
 <link rel="import" href="/certificate_manager_page/certificates_browser_proxy.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-certificate-subentry">
   <template>
     <style include="settings-shared">
       .dropdown-content {
         background: white;
         /* TODO(dpapad): Use a CSS variable for box-shadow and unify with other
          *  such menus (like in search engines section) */
         box-shadow: 0 2px 6px grey;
       }
 
       .name {
         flex: auto;
       }
 
       .untrusted {
         -webkit-margin-end: 16px;
         color: var(--settings-error-color);
         font-weight: 500;
         text-transform: uppercase;
       }
 
-      paper-item:hover {
-        background-color: var(--settings-hover-color);
-      }
-
       :host([is-last]) .list-item {
         border-bottom: none;
       }
     </style>
     <div class="list-item underbar">
       <div class="untrusted" hidden$="[[!model.untrusted]]">
         $i18n{certificateManagerUntrusted}
       </div>
       <div class="name">[[model.name]]</div>
       <paper-icon-button id="dots" icon="cr:more-vert" toggles
           active="{{menuOpened}}"></paper-icon-button>
       <!-- TODO(dpapad): Figure out RTL for this menu -->
       <template is="dom-if" if="[[menuOpened]]">
         <iron-dropdown vertical-align="auto" horizontal-align="right"
             opened="{{menuOpened}}">
           <div class="dropdown-content">
-            <paper-item id="view" on-tap="onViewTap_">
+            <button class="dropdown-item" role="option" id="view"
+                on-tap="onViewTap_">
               $i18n{certificateManagerView}
-            </paper-item>
-            <paper-item id="edit" hidden$="[[!canEdit_(certificateType, model)]]"
+            </button>
+            <button class="dropdown-item" role="option" id="edit"
+                hidden$="[[!canEdit_(certificateType, model)]]"
                 on-tap="onEditTap_">
               $i18n{certificateManagerEdit}
-            </paper-item>
-            <paper-item id="export"
+            </button>
+            <button class="dropdown-item" role="option" id="export"
                 hidden$="[[!canExport_(certificateType, model)]]"
                 on-tap="onExportTap_">
               $i18n{certificateManagerExport}
-            </paper-item>
-            <paper-item id="delete" hidden$="[[!canDelete_(model)]]"
-                on-tap="onDeleteTap_">
+            </button>
+            <button class="dropdown-item" role="option" id="delete"
+                hidden$="[[!canDelete_(model)]]" on-tap="onDeleteTap_">
               $i18n{certificateManagerDelete}
-            </paper-item>
+            </button>
           </div>
         </iron-dropdown>
       </template>
     <div>
   </template>
   <script src="certificate_subentry.js"></script>
 </dom-module>