MD Settings: Enable to search "Add languages" list.

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

 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/iron-input/iron-input.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-input/paper-input-container.html">

[michaelpg, 2016/12/01 20:40:13]

alphabetize (move below paper-checkbox)

 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
 <link rel="import" href="/languages_page/languages.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-add-languages-dialog">
   <template>
     <style include="settings-shared">
       dialog {
         display: flex;
         flex-direction: column;
       }
 
       .body {
         display: flex;
         flex-direction: column;
         max-height: 250px;
         overflow: auto;
       }
 
       .ripple-padding {
         /* Create a little extra space for checkbox ink ripple to flow into. */
         padding-left: 20px;
       }
     </style>
     <dialog is="cr-dialog" id="dialog">
       <div class="title">$i18n{addLanguagesDialogTitle}</div>
       <div class="body">
-        <!-- TODO(michaelpg): Dynamic language search/filtering. -->
-        <iron-list class="ripple-padding" scroll-target="[[$$('.body')]]"
+        <paper-input-container>

[michaelpg, 2016/12/02 03:56:41]

+dpapad to figure out the best way to add a filter to a dialog, a la
settings-subpage-search.

In particular, how to keep the padding correct: changing the scroll-target (line
37) shrinks the area that scrolls, so the scroller looks like it's in the wrong
position (the current scrollbar position was explicitly requested).

+          <input is="iron-input" bind-value="{{filterValue_}}">
+        </paper-input-container>
+        <iron-list class="ripple-padding" scroll-target="[[$$('.ripple-padding')]]"

[michaelpg, 2016/12/01 20:40:13]

keep to 80-column lines (e.g., break before scroll-target)

             items="[[getAvailableLanguages_(
-                languages.supported, languages.enabled.*)]]">
+                languages.supported, languages.enabled.*, filterValue_)]]">
           <template>
             <paper-checkbox class="list-item" checked="[[willAdd_(item.code)]]"
                 title$="[[item.nativeDisplayName]]"
                 on-change="onLanguageCheckboxChange_">
               [[item.displayName]]
             </paper-checkbox>
           </template>
         </iron-list>
       </div>
       <div class="button-container">
         <div class="action-buttons">
           <paper-button class="cancel-button" on-tap="onCancelButtonTap_">
             $i18n{cancel}
           </paper-button>
           <paper-button class="action-button" on-tap="onActionButtonTap_"
               disabled="[[disableActionButton_]]">
             $i18n{add}
           </paper-button>
         </div>
       </div>
     </dialog>
   </template>
   <script src="add_languages_dialog.js"></script>
 </dom-module>