Polymer 2: Add _legacyUndefinedCheck

When legacy-data-mixin.html is imported this will tell you on the console which observers need fixing regarding this change of behavior:

https://polymer-library.polymer-project.org/2.0/docs/upgrade#update-observers

This change was created by running this command line:

find polygerrit-ui/app/ -type f | xargs sed -i '/^    is: / a\    _legacyUndefinedCheck: true,'

Once all observers are fixed, this change will be reverted. This is tracked in https://bugs.chromium.org/p/gerrit/issues/detail?id=10723

Change-Id: Icccdfaa52bf77dfb25e949b2aa2402110f6c2276

polygerrit-ui/app/behaviors/base-url-behavior/base-url-behavior_test.html

@@ -52,6 +52,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [
           Gerrit.BaseUrlBehavior,
         ],

polygerrit-ui/app/behaviors/docs-url-behavior/docs-url-behavior_test.html

@@ -38,6 +38,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'docs-url-behavior-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.DocsUrlBehavior],
       });
     });

polygerrit-ui/app/behaviors/dom-util-behavior/dom-util-behavior_test.html

@@ -46,6 +46,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.DomUtilBehavior],
       });
     });

polygerrit-ui/app/behaviors/gr-access-behavior/gr-access-behavior_test.html

@@ -38,6 +38,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.AccessBehavior],
       });
     });

polygerrit-ui/app/behaviors/gr-admin-nav-behavior/gr-admin-nav-behavior_test.html

@@ -41,6 +41,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [
           Gerrit.AdminNavBehavior,
         ],

polygerrit-ui/app/behaviors/gr-anonymous-name-behavior/gr-anonymous-name-behavior_test.html

@@ -44,6 +44,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element-anon',
+        _legacyUndefinedCheck: true,
         behaviors: [
           Gerrit.AnonymousNameBehavior,
         ],

polygerrit-ui/app/behaviors/gr-change-table-behavior/gr-change-table-behavior_test.html

@@ -48,6 +48,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.ChangeTableBehavior],
       });
     });

polygerrit-ui/app/behaviors/gr-list-view-behavior/gr-list-view-behavior_test.html

@@ -40,6 +40,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.ListViewBehavior],
       });
     });

polygerrit-ui/app/behaviors/gr-tooltip-behavior/gr-tooltip-behavior_test.html

@@ -51,6 +51,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'tooltip-behavior-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.TooltipBehavior],
       });
     });

polygerrit-ui/app/behaviors/gr-url-encoding-behavior/gr-url-encoding-behavior_test.html

@@ -40,6 +40,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.URLEncodingBehavior],
       });
     });

polygerrit-ui/app/behaviors/keyboard-shortcut-behavior/keyboard-shortcut-behavior_test.html

@@ -50,6 +50,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.KeyboardShortcutBehavior],
         keyBindings: {
           k: '_handleKey',

polygerrit-ui/app/behaviors/rest-client-behavior/rest-client-behavior_test.html

@@ -54,6 +54,7 @@ limitations under the License.
       // Define a Polymer element that uses this behavior.
       Polymer({
         is: 'test-element',
+        _legacyUndefinedCheck: true,
         behaviors: [
           Gerrit.BaseUrlBehavior,
           Gerrit.RESTClientBehavior,

polygerrit-ui/app/behaviors/safe-types-behavior/safe-types-behavior_test.html

@@ -39,6 +39,7 @@ limitations under the License.
     suiteSetup(() => {
       Polymer({
         is: 'safe-types-element',
+        _legacyUndefinedCheck: true,
         behaviors: [Gerrit.SafeTypes],
       });
     });

polygerrit-ui/app/elements/admin/gr-access-section/gr-access-section.js

@@ -38,6 +38,7 @@
 
   Polymer({
     is: 'gr-access-section',
+    _legacyUndefinedCheck: true,
 
     properties: {
       capabilities: Object,

polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-admin-group-list',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /**

polygerrit-ui/app/elements/admin/gr-admin-view/gr-admin-view.js

@@ -22,6 +22,7 @@
 
   Polymer({
     is: 'gr-admin-view',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {?} */

polygerrit-ui/app/elements/admin/gr-confirm-delete-item-dialog/gr-confirm-delete-item-dialog.js

@@ -25,6 +25,7 @@
 
   Polymer({
     is: 'gr-confirm-delete-item-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/admin/gr-create-change-dialog/gr-create-change-dialog.js

@@ -22,6 +22,7 @@
 
   Polymer({
     is: 'gr-create-change-dialog',
+    _legacyUndefinedCheck: true,
 
     properties: {
       repoName: String,

polygerrit-ui/app/elements/admin/gr-create-group-dialog/gr-create-group-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-create-group-dialog',
+    _legacyUndefinedCheck: true,
 
     properties: {
       params: Object,

polygerrit-ui/app/elements/admin/gr-create-pointer-dialog/gr-create-pointer-dialog.js

@@ -24,6 +24,7 @@
 
   Polymer({
     is: 'gr-create-pointer-dialog',
+    _legacyUndefinedCheck: true,
 
     properties: {
       detailType: String,

polygerrit-ui/app/elements/admin/gr-create-repo-dialog/gr-create-repo-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-create-repo-dialog',
+    _legacyUndefinedCheck: true,
 
     properties: {
       params: Object,

polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-group-audit-log',
+    _legacyUndefinedCheck: true,
 
     properties: {
       groupId: String,

polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.js

@@ -25,6 +25,7 @@
 
   Polymer({
     is: 'gr-group-members',
+    _legacyUndefinedCheck: true,
 
     properties: {
       groupId: Number,

polygerrit-ui/app/elements/admin/gr-group/gr-group.js

@@ -32,6 +32,7 @@
 
   Polymer({
     is: 'gr-group',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the group name changes.

polygerrit-ui/app/elements/admin/gr-permission/gr-permission.js

@@ -37,6 +37,7 @@
 
   Polymer({
     is: 'gr-permission',
+    _legacyUndefinedCheck: true,
 
     properties: {
       labels: Object,

polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-plugin-list',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /**

polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.js

@@ -70,6 +70,7 @@
 
   Polymer({
     is: 'gr-repo-access',
+    _legacyUndefinedCheck: true,
 
     properties: {
       repo: {

polygerrit-ui/app/elements/admin/gr-repo-command/gr-repo-command.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-repo-command',
+    _legacyUndefinedCheck: true,
 
     properties: {
       title: String,

polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.js

@@ -28,6 +28,7 @@
 
   Polymer({
     is: 'gr-repo-commands',
+    _legacyUndefinedCheck: true,
 
     properties: {
       params: Object,

polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-repo-dashboards',
+    _legacyUndefinedCheck: true,
 
     properties: {
       repo: {

polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.js

@@ -26,6 +26,7 @@
 
   Polymer({
     is: 'gr-repo-detail-list',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /**

polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-repo-list',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /**

polygerrit-ui/app/elements/admin/gr-repo/gr-repo.js

@@ -53,6 +53,7 @@
 
   Polymer({
     is: 'gr-repo',
+    _legacyUndefinedCheck: true,
 
     properties: {
       params: Object,

polygerrit-ui/app/elements/admin/gr-rule-editor/gr-rule-editor.js

@@ -65,6 +65,7 @@
 
   Polymer({
     is: 'gr-rule-editor',
+    _legacyUndefinedCheck: true,
 
     properties: {
       hasRange: Boolean,

polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item.js

@@ -26,6 +26,7 @@
 
   Polymer({
     is: 'gr-change-list-item',
+    _legacyUndefinedCheck: true,
 
     properties: {
       visibleChangeTableColumns: Array,

polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.js

@@ -31,6 +31,7 @@
 
   Polymer({
     is: 'gr-change-list-view',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the title of the page should change.

polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js

@@ -24,6 +24,7 @@
 
   Polymer({
     is: 'gr-change-list',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when next page key shortcut was pressed.

polygerrit-ui/app/elements/change-list/gr-create-change-help/gr-create-change-help.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-create-change-help',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the "Create change" button is tapped.

polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog.js

@@ -25,6 +25,7 @@
 
   Polymer({
     is: 'gr-create-commands-dialog',
+    _legacyUndefinedCheck: true,
     properties: {
       branch: String,
       _createNewCommitCommand: {

polygerrit-ui/app/elements/change-list/gr-create-destination-dialog/gr-create-destination-dialog.js

@@ -26,6 +26,7 @@
 
   Polymer({
     is: 'gr-create-destination-dialog',
+    _legacyUndefinedCheck: true,
     properties: {
       _repo: String,
       _branch: String,

polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-dashboard-view',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the title of the page should change.

polygerrit-ui/app/elements/change-list/gr-embed-dashboard/gr-embed-dashboard.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-embed-dashboard',
+    _legacyUndefinedCheck: true,
     properties: {
       account: Object,
       sections: Array,

polygerrit-ui/app/elements/change-list/gr-repo-header/gr-repo-header.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-repo-header',
+    _legacyUndefinedCheck: true,
     properties: {
       /** @type {?String} */
       repo: {

polygerrit-ui/app/elements/change-list/gr-user-header/gr-user-header.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-user-header',
+    _legacyUndefinedCheck: true,
     properties: {
       /** @type {?String} */
       userId: {

polygerrit-ui/app/elements/change/gr-account-entry/gr-account-entry.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-account-entry',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when an account is entered.

polygerrit-ui/app/elements/change/gr-account-list/gr-account-list.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-account-list',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when user inputs an invalid email address.

polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js

@@ -193,6 +193,7 @@
 
   Polymer({
     is: 'gr-change-actions',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the change should be reloaded.

polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.js

@@ -61,6 +61,7 @@
 
   Polymer({
     is: 'gr-change-metadata',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the change topic is changed.

polygerrit-ui/app/elements/change/gr-change-requirements/gr-change-requirements.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-change-requirements',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {?} */

polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js

@@ -64,6 +64,7 @@
 
   Polymer({
     is: 'gr-change-view',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the title of the page should change.

polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js

@@ -18,6 +18,7 @@
   'use strict';
   Polymer({
     is: 'gr-comment-list',
+    _legacyUndefinedCheck: true,
 
     behaviors: [
       Gerrit.BaseUrlBehavior,

polygerrit-ui/app/elements/change/gr-commit-info/gr-commit-info.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-commit-info',
+    _legacyUndefinedCheck: true,
 
     properties: {
       change: Object,

polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-confirm-abandon-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-confirm-cherrypick-conflict-dialog/gr-confirm-cherrypick-conflict-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-confirm-cherrypick-conflict-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-confirm-cherrypick-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-confirm-move-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-confirm-rebase-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js

@@ -22,6 +22,7 @@
 
   Polymer({
     is: 'gr-confirm-revert-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-confirm-submit-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.

polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-download-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.

polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js

@@ -23,6 +23,7 @@
 
   Polymer({
     is: 'gr-file-list-header',
+    _legacyUndefinedCheck: true,
 
     /**
      * @event expand-diffs

polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js

@@ -63,6 +63,7 @@
 
   Polymer({
     is: 'gr-file-list',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a draft refresh should get triggered

polygerrit-ui/app/elements/change/gr-included-in-dialog/gr-included-in-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-included-in-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.

polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-label-score-row',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when any label is changed.

polygerrit-ui/app/elements/change/gr-label-scores/gr-label-scores.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-label-scores',
+    _legacyUndefinedCheck: true,
     properties: {
       _labels: {
         type: Array,

polygerrit-ui/app/elements/change/gr-message/gr-message.js

@@ -22,6 +22,7 @@
 
   Polymer({
     is: 'gr-message',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when this message's reply link is tapped.

polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.js

@@ -27,6 +27,7 @@
 
   Polymer({
     is: 'gr-messages-list',
+    _legacyUndefinedCheck: true,
 
     properties: {
       changeNum: Number,

polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-related-changes-list',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a new section is loaded so that the change view can determine

polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js

@@ -58,6 +58,7 @@
 
   Polymer({
     is: 'gr-reply-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a reply is successfully sent.

polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-reviewer-list',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the "Add reviewer..." button is tapped.

polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.js

@@ -25,6 +25,7 @@
 
   Polymer({
     is: 'gr-thread-list',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {?} */

polygerrit-ui/app/elements/change/gr-upload-help-dialog/gr-upload-help-dialog.js

@@ -29,6 +29,7 @@
 
   Polymer({
     is: 'gr-upload-help-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.

polygerrit-ui/app/elements/core/gr-account-dropdown/gr-account-dropdown.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-account-dropdown',
+    _legacyUndefinedCheck: true,
 
     properties: {
       account: Object,

polygerrit-ui/app/elements/core/gr-error-dialog/gr-error-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-error-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the dismiss button is pressed.

polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.js

@@ -27,6 +27,7 @@
 
   Polymer({
     is: 'gr-error-manager',
+    _legacyUndefinedCheck: true,
 
     behaviors: [
       Gerrit.BaseUrlBehavior,

polygerrit-ui/app/elements/core/gr-key-binding-display/gr-key-binding-display.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-key-binding-display',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {Array<string>} */

polygerrit-ui/app/elements/core/gr-keyboard-shortcuts-dialog/gr-keyboard-shortcuts-dialog.js

@@ -21,6 +21,7 @@
 
   Polymer({
     is: 'gr-keyboard-shortcuts-dialog',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.

polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.js

@@ -71,6 +71,7 @@
 
   Polymer({
     is: 'gr-main-header',
+    _legacyUndefinedCheck: true,
 
     hostAttributes: {
       role: 'banner',

polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js

@@ -144,6 +144,7 @@
   // eslint-disable-next-line prefer-const
   let GrReporting = Polymer({
     is: 'gr-reporting',
+    _legacyUndefinedCheck: true,
 
     properties: {
       category: String,

polygerrit-ui/app/elements/core/gr-router/gr-router.js

@@ -204,6 +204,7 @@
 
   Polymer({
     is: 'gr-router',
+    _legacyUndefinedCheck: true,
 
     properties: {
       _app: {

polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.js

@@ -106,6 +106,7 @@
 
   Polymer({
     is: 'gr-search-bar',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a search is committed

polygerrit-ui/app/elements/core/gr-smart-search/gr-smart-search.js

@@ -23,6 +23,7 @@
 
   Polymer({
     is: 'gr-smart-search',
+    _legacyUndefinedCheck: true,
 
     properties: {
       searchQuery: String,

polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api-mock.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'comment-api-mock',
+    _legacyUndefinedCheck: true,
 
     properties: {
       _changeComments: Object,

polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.js

@@ -482,6 +482,7 @@
 
   Polymer({
     is: 'gr-comment-api',
+    _legacyUndefinedCheck: true,
 
     properties: {
       _changeComments: Object,

polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.html

@@ -65,6 +65,7 @@ limitations under the License.
 
       Polymer({
         is: 'gr-diff-builder',
+        _legacyUndefinedCheck: true,
 
         /**
          * Fired when the diff begins rendering.

polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.js

@@ -37,6 +37,7 @@
 
   Polymer({
     is: 'gr-diff-cursor',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /**

polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-diff-highlight',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {!Array<!Gerrit.HoveredRange>} */

polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.js

@@ -66,6 +66,7 @@
    */
   Polymer({
     is: 'gr-diff-host',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user selects a line.

polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-diff-mode-selector',
+    _legacyUndefinedCheck: true,
 
     properties: {
       mode: {

polygerrit-ui/app/elements/diff/gr-diff-preferences-dialog/gr-diff-preferences-dialog.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-diff-preferences-dialog',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {?} */

polygerrit-ui/app/elements/diff/gr-diff-processor/gr-diff-processor.js

@@ -60,6 +60,7 @@
    */
   Polymer({
     is: 'gr-diff-processor',
+    _legacyUndefinedCheck: true,
 
     properties: {
 

polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js

@@ -32,6 +32,7 @@
 
   Polymer({
     is: 'gr-diff-selection',
+    _legacyUndefinedCheck: true,
 
     properties: {
       diff: Object,

polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js

@@ -35,6 +35,7 @@
 
   Polymer({
     is: 'gr-diff-view',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the title of the page should change.

polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js

@@ -106,6 +106,7 @@
 
   Polymer({
     is: 'gr-diff',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user selects a line.

polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.js

@@ -31,6 +31,7 @@
 
   Polymer({
     is: 'gr-patch-range-select',
+    _legacyUndefinedCheck: true,
 
     properties: {
       availablePatches: Array,

polygerrit-ui/app/elements/diff/gr-ranged-comment-layer/gr-ranged-comment-layer.js

@@ -27,6 +27,7 @@
 
   Polymer({
     is: 'gr-ranged-comment-layer',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the range in a range comment was malformed and had to be

polygerrit-ui/app/elements/diff/gr-selection-action-box/gr-selection-action-box.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-selection-action-box',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the comment creation action was taken (hotkey, click).

polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js

@@ -129,6 +129,7 @@
 
   Polymer({
     is: 'gr-syntax-layer',
+    _legacyUndefinedCheck: true,
 
     properties: {
       diff: {

polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-documentation-search',
+    _legacyUndefinedCheck: true,
 
     properties: {
       /**

polygerrit-ui/app/elements/edit/gr-default-editor/gr-default-editor.js

@@ -19,6 +19,7 @@
 
   Polymer({
     is: 'gr-default-editor',
+    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the content of the editor changes.