Hide the DIV containing password import/export buttons

The import/export feature for passwords is currently behind a flag. However,
the settings WebUI hides the controls instead of the containing DIV. As a
result, on loading the settings, the space for the controls is briefly
taken into consideration and a vertical scrollbar shows up.

This CL hides the containing DIV instead of the individual controls.

Test steps:
With chrome://flags/#password-import-export enabled, observe that about:settings/passwords looks the same as without the patch. With chrome://flags/#password-import-export disabled, observe that during reloading of about:settings/passwords, no vertical scroll bar is flashing/seen.

BUG=626634
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2154223002
Cr-Commit-Position: refs/heads/master@{#406616}

chrome/browser/resources/options/password_manager.html

@@ -28,13 +28,13 @@
         <a target="_blank" i18n-content="learnMore"
            i18n-values="href:passwordManagerLearnMoreURL"></a>
       </div>
-      <div class="action-area">
+      <div id="password-manager-import-export" class="action-area" hidden>
         <div class="button-strip">
           <button id="password-manager-import" class="password-manager-home"
-              i18n-content="passwordManagerImportPasswordButtonText" hidden>
+              i18n-content="passwordManagerImportPasswordButtonText">
           </button>
           <button id="password-manager-export" class="password-manager-home"
-              i18n-content="passwordManagerExportPasswordButtonText" hidden>
+              i18n-content="passwordManagerExportPasswordButtonText">
           </button>
         </div>
       </div>

chrome/browser/resources/options/password_manager.js

@@ -289,8 +289,7 @@ cr.define('options', function() {
 
     /** @private */
     showImportExportButton_: function() {
-      $('password-manager-import').hidden = false;
-      $('password-manager-export').hidden = false;
+      $('password-manager-import-export').hidden = false;
     },
   };