Revert partially "cros: Use AlertDialog for remora device requisition."

This reverts the webui change from the commit 9cc0da7d (https://codereview.chromium.org/61523002/).
The reverted webui change breaks alert dialogs in the Files app by making them not closable by pressing the Escape key.

TEST=Tested manually in Files app.
BUG=330835, 331739

Review URL: https://codereview.chromium.org/129973002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244064 0039d316-1c4b-4281-b951-d872f2087c98

ui/webui/resources/js/cr/ui/dialogs.js

@@ -91,9 +91,7 @@ cr.define('cr.ui.dialogs', function() {
 
   BaseDialog.prototype.onContainerKeyDown_ = function(event) {
     // Handle Escape.
-    if (event.keyCode == 27 &&
-        !this.cancelButton_.disabled &&
-        !this.cancelButton_.hidden) {
+    if (event.keyCode == 27 && !this.cancelButton_.disabled) {
       this.onCancelClick_(event);
       event.stopPropagation();
       // Prevent the event from being handled by the container of the dialog.
@@ -244,8 +242,7 @@ cr.define('cr.ui.dialogs', function() {
    */
   function AlertDialog(parentNode) {
     BaseDialog.apply(this, [parentNode]);
-    this.cancelButton_.hidden = true;
-    this.closeButton_.hidden = true;
+    this.cancelButton_.style.display = 'none';
   }
 
   AlertDialog.prototype = {__proto__: BaseDialog.prototype};