Implement "Autofill form data" import for Firefox

chrome/browser/resources/options/import_data_overlay.html

 <div id="import-data-overlay" class="page" hidden>
   <div class="close-button"></div>
   <h1 i18n-content="importDataOverlay"></h1>
   <div class="content-area">
     <div class="import-data-configure">
       <div id="import-from-div">
         <span i18n-content="importFromLabel"></span>
         <select id="import-browsers">
           <option i18n-content="importLoading"></option>
         </select>
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         <div class="checkbox controlled-setting-with-label"
             id="import-search-with-label">
           <label>
             <input id="import-search" type="checkbox"
                 pref="import_search_engine">
             <span i18n-content="importSearch"></span>
           </label>
           <span class="controlled-setting-indicator"
               pref="import_search_engine"></span>
         </div>
+        <div class="checkbox controlled-setting-with-label"
+            id="import-autofill-form-data-with-label">
+          <label>
+            <input id="import-autofill-form-data" type="checkbox"
+                pref="import_autofill_form_data">
+            <span i18n-content="importAutofillFormData"></span>
+          </label>
+          <span class="controlled-setting-indicator"
+              pref="import_autofill_form_data"></span>
+        </div>
       </div>
     </div>
     <div class="import-data-success" hidden>
       <div id="import-success-header">
         <strong i18n-content="importSucceeded"></strong>
       </div>
       <div id="import-success-image">
         <img src="../../../../ui/webui/resources/images/success.png">
       </div>
       <div id="import-find-your-bookmarks">
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         </div>
       </div>
     </div>
   </div>
 <if expr="is_macosx">
   <div id="mac-password-keychain" class="gray-bottom-bar">
     <span i18n-content="macPasswordKeychain"></span>
   </div>
 </if>
 </div>