Language settings: Fix unnecessarily shown move buttons

chrome/browser/resources/settings/languages_page/languages_page.html

 <link rel="import" href="chrome://resources/html/action_link.html">
 <link rel="import" href="chrome://resources/html/action_link_css.html">
 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-collapse/iron-collapse.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_action_menu/cr_action_menu.html">
@@ skipping 221 matching lines @@
                 checked="[[detailLanguage_.translateEnabled]]"
                 on-change="onTranslateCheckboxChange_"
                 hidden="[[!prefs.translate.enabled.value]]"
                 disabled="[[disableTranslateCheckbox_(
                     detailLanguage_.language, languages.translateTarget)]]">
               $i18n{offerToTranslateInThisLanguage}
             </paper-checkbox>
             <hr>
             <button class="dropdown-item" role="menuitem"
                 on-tap="onMoveToTopTap_"
-                hidden="[[isFirstLanguage_(
-                    detailLanguage_, languages.enabled.*)]]">
+                hidden="[[isNthLanguage_(
+                    0, detailLanguage_, languages.enabled.*)]]">
               $i18n{moveToTop}
             </button>
             <button class="dropdown-item" role="menuitem"
                 on-tap="onMoveUpTap_"
-                hidden="[[isFirstOrSecondLanguage_(
-                    detailLanguage_, languages.enabled.*)]]">
+                hidden="[[!showMoveUp_(detailLanguage_, languages.enabled.*)]]">
               $i18n{moveUp}
             </button>
             <button class="dropdown-item" role="menuitem"
                 on-tap="onMoveDownTap_"
-                hidden="[[isLastLanguage_(
+                hidden="[[!showMoveDown_(
                     detailLanguage_, languages.enabled.*)]]">
               $i18n{moveDown}
             </button>
             <button class="dropdown-item" role="menuitem"
                 on-tap="onRemoveLanguageTap_"
                 hidden="[[!detailLanguage_.removable]]">
               $i18n{removeLanguage}
             </button>
           </dialog>
         </template>
@@ skipping 20 matching lines @@
 </if>
     </settings-animated-pages>
     <template is="dom-if" if="[[showAddLanguagesDialog_]]" restamp>
       <settings-add-languages-dialog languages="{{languages}}"
           language-helper="[[languageHelper]]">
       </settings-add-languages-dialog>
     </template>
   </template>
   <script src="languages_page.js"></script>
 </dom-module>