[sync] Separate sign in from sync on Desktop Chrome

chrome/browser/resources/sync_setup_overlay.html

 <div id="sync-setup-overlay" class="page" hidden>
   <div class="close-button"></div>
   <div id="sync-setup-login" hidden>
     <div id="promo-title-container" hidden>
       <h1 i18n-content="promoTitle"></h1>
       <h2>
         <span i18n-content="promoTitleShort"></span>
         <a id="promo-learn-more" i18n-content="promoLearnMore"
             i18n-values="href:promoLearnMoreURL">
         </a>
@@ skipping 160 matching lines @@
       </div>
     </div>
     <div id="customize-sync-preferences" hidden>
       <h1 i18n-content="syncSetupConfigureTitle"></h1>
       <form id="choose-data-types-form">
         <div id="sync-configure-content" class="content-area">
           <div id="sync-select-container">
             <select id="sync-select-datatypes">
               <option i18n-content="syncAllDataTypes" selected></option>
               <option i18n-content="chooseDataTypes"></option>
+              <option i18n-content="syncNothing"></option>
             </select>
             <div id="choose-data-types-body">
               <div id="apps-item" class="sync-type-checkbox checkbox">
                 <label>
                   <input id="apps-checkbox" type="checkbox">
                   <span i18n-content="apps" i18n-values="title:apps"></span>
                 </label>
               </div>
               <div id="autofill-item" class="sync-type-checkbox checkbox">
                 <label>
@@ skipping 214 matching lines @@
       <span i18n-values=".innerHTML:stopSyncingExplanation"></span>
     </div>
     <div class="action-area button-strip">
       <input id="stop-syncing-cancel" type="button"
           i18n-values="value:cancel">
       <input id="stop-syncing-ok" type="button"
           i18n-values="value:stopSyncingConfirm">
     </div>
   </div>
 </div>