MD Settings: add 'preserve-focus' flag to fix iron-list focus bugs.

chrome/browser/resources/settings/languages_page/edit_dictionary_page.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-a11y-keys/iron-a11y-keys.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="../global_scroll_target_behavior.html">
 <link rel="import" href="../prefs/prefs.html">
@@ skipping 30 matching lines @@
       <paper-button class="secondary-button" on-tap="onAddWordTap_"
           disabled="[[!validateWord_(newWordValue_)]]" id="addWord">
         $i18n{addDictionaryWordButton}
       </paper-button>
     </div>
     <div class="settings-box continuation block">
       <h2>$i18n{customDictionaryWords}</h2>
     </div>
     <div class="list-frame">
       <template is="dom-if" if="[[hasWords_(words_.length)]]">
-        <iron-list id="list" items="[[words_]]"
+        <iron-list id="list" items="[[words_]]" preserve-focus
             scroll-target="[[subpageScrollTarget]]">
           <template>
             <div class="list-item">
               <div class="word text-elide">[[item]]</div>
               <button is="paper-icon-button-light" class="icon-clear"
                   on-tap="onRemoveWordTap_" tabindex$="[[tabIndex]]">
               </button>
             </div>
           </template>
         </iron-list>
       </template>
       <template is="dom-if" if="[[!hasWords_(words_.length)]]">
         <div id="noWordsLabel" class="list-item">
           $i18n{noCustomDictionaryWordsFound}
         </div>
       </template>
     </div>
   </template>
   <script src="edit_dictionary_page.js"></script>
 </dom-module>