Put Sync Encryption UI behind command line switch.

chrome/browser/resources/options/sync_setup_overlay.html

 <div id="sync-setup-overlay" class="page hidden">
   <div id="sync-setup-login" class="hidden">
     <h1 i18n-content="syncSetupOverlayTitle"></h1>
     <div class="content-area">
       <div>
         <div id="top-blurb-error">
           <span id="error-signing-in" i18n-content="errorSigningIn"></span>
           <span id="error-custom"></span>
         </div>
         <form id="gaia-login-form">
@@ skipping 272 matching lines @@
                 </div>
               </div>
             </div>
           </div>
           <div class="sync-errors">
             <span id="error-text" i18n-content="syncZeroDataTypesError"
                 class="sync-error-hide"></span>
             <span id="aborted-text" i18n-content="abortedError"
                 class="sync-error-hide"></span>
           </div>
+          <div id="customize-sync-encryption">
           <hr>
-          <h4 i18n-content="encryptedDataTypesTitle"></h4>
-          <div class="sync-customize-section-container">
-            <div>
-              <input id="encrypt-sensitive-option" name="encrypt" type="radio"
-                  value="sensitive">
-              <label for="encrypt-sensitive-option"
-                  i18n-content="encryptSensitiveOption"></label>
-            </div>
-            <div>
-              <input id="encrypt-all-option" name="encrypt" type="radio"
-                  value="all">
-              <label for="encrypt-all-option" i18n-content="encryptAllOption">
-              </label>
+            <h4 i18n-content="encryptedDataTypesTitle"></h4>
+            <div class="sync-customize-section-container">
+              <div>
+                <input id="encrypt-sensitive-option" name="encrypt" type="radio"
+                    value="sensitive">
+                <label for="encrypt-sensitive-option"
+                    i18n-content="encryptSensitiveOption"></label>
+              </div>
+              <div>
+                <input id="encrypt-all-option" name="encrypt" type="radio"
+                    value="all">
+                <label for="encrypt-all-option" i18n-content="encryptAllOption">
+                </label>
+              </div>
             </div>
           </div>
           <hr>
           <h4 i18n-content="passphraseSectionTitle"></h4>
           <div class="sync-customize-section-container">
             <div id="passphrase-encryption-message"
                 i18n-content="passphraseEncryptionMessage"></div>
             <div>
               <input id="google-option" name="option" type="radio"
                   value="google">
@@ skipping 74 matching lines @@
         </div>
       </form>
     </div>
     <div class="action-area">
       <div id="passphrase-throbber" class="throbber"></div>
       <input id="passphrase-ok" type="submit" i18n-values="value:ok">
       <input id="passphrase-cancel" type="button" i18n-values="value:cancel">
     </div>
   </div>
 </div>