diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
index 3b09270a4b..8fa9f60a83 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
@@ -193,7 +193,6 @@
 
   Polymer({
     is: 'gr-change-actions',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the change should be reloaded.
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.js b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.js
index 9788975747..6632b8e48d 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.js
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.js
@@ -61,7 +61,6 @@
 
   Polymer({
     is: 'gr-change-metadata',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the change topic is changed.
diff --git a/polygerrit-ui/app/elements/change/gr-change-requirements/gr-change-requirements.js b/polygerrit-ui/app/elements/change/gr-change-requirements/gr-change-requirements.js
index 09efa8d491..8ec00dd710 100644
--- a/polygerrit-ui/app/elements/change/gr-change-requirements/gr-change-requirements.js
+++ b/polygerrit-ui/app/elements/change/gr-change-requirements/gr-change-requirements.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-change-requirements',
-    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {?} */
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
index 1627999aaf..94f60b11a0 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
@@ -65,7 +65,6 @@
 
   Polymer({
     is: 'gr-change-view',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the title of the page should change.
diff --git a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js
index 660dfd9f52..cbc7e429b6 100644
--- a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js
+++ b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js
@@ -18,7 +18,6 @@
   'use strict';
   Polymer({
     is: 'gr-comment-list',
-    _legacyUndefinedCheck: true,
 
     behaviors: [
       Gerrit.BaseUrlBehavior,
diff --git a/polygerrit-ui/app/elements/change/gr-commit-info/gr-commit-info.js b/polygerrit-ui/app/elements/change/gr-commit-info/gr-commit-info.js
index 7e25180522..e2fcdffb2c 100644
--- a/polygerrit-ui/app/elements/change/gr-commit-info/gr-commit-info.js
+++ b/polygerrit-ui/app/elements/change/gr-commit-info/gr-commit-info.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-commit-info',
-    _legacyUndefinedCheck: true,
 
     properties: {
       change: Object,
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js
index f83ea8f964..524876e21f 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-confirm-abandon-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-conflict-dialog/gr-confirm-cherrypick-conflict-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-conflict-dialog/gr-confirm-cherrypick-conflict-dialog.js
index 195027a04e..a0da331fa3 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-conflict-dialog/gr-confirm-cherrypick-conflict-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-conflict-dialog/gr-confirm-cherrypick-conflict-dialog.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-confirm-cherrypick-conflict-dialog',
-    _legacyUndefinedCheck: true,
 
     behaviors: [
       Gerrit.FireBehavior,
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js
index 61597421a8..bf8400379f 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js
@@ -21,7 +21,6 @@
 
   Polymer({
     is: 'gr-confirm-cherrypick-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.js
index 3636c9e74f..23123c3e3b 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.js
@@ -21,7 +21,6 @@
 
   Polymer({
     is: 'gr-confirm-move-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js
index a2fef69893..414182c3c9 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-confirm-rebase-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
index c064d14957..662b64c349 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
@@ -22,7 +22,6 @@
 
   Polymer({
     is: 'gr-confirm-revert-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js
index 6b4a886c41..e86e21c5d1 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-confirm-submit-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the confirm button is pressed.
diff --git a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.js b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.js
index 4fe902bd87..90cc60f84b 100644
--- a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-download-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.
diff --git a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js
index 870be8b917..212643329b 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js
@@ -23,7 +23,6 @@
 
   Polymer({
     is: 'gr-file-list-header',
-    _legacyUndefinedCheck: true,
 
     /**
      * @event expand-diffs
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
index 6b84901ad4..914b4eb927 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
@@ -63,7 +63,6 @@
 
   Polymer({
     is: 'gr-file-list',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a draft refresh should get triggered
diff --git a/polygerrit-ui/app/elements/change/gr-included-in-dialog/gr-included-in-dialog.js b/polygerrit-ui/app/elements/change/gr-included-in-dialog/gr-included-in-dialog.js
index 2b7dcb6abd..4b8ce2256f 100644
--- a/polygerrit-ui/app/elements/change/gr-included-in-dialog/gr-included-in-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-included-in-dialog/gr-included-in-dialog.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-included-in-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.
diff --git a/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row.js b/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row.js
index a77b62421b..2ea63b04fb 100644
--- a/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row.js
+++ b/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-label-score-row',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when any label is changed.
diff --git a/polygerrit-ui/app/elements/change/gr-label-scores/gr-label-scores.js b/polygerrit-ui/app/elements/change/gr-label-scores/gr-label-scores.js
index 548798ff63..5b498c202b 100644
--- a/polygerrit-ui/app/elements/change/gr-label-scores/gr-label-scores.js
+++ b/polygerrit-ui/app/elements/change/gr-label-scores/gr-label-scores.js
@@ -19,7 +19,7 @@
 
   Polymer({
     is: 'gr-label-scores',
-    _legacyUndefinedCheck: true,
+
     properties: {
       _labels: {
         type: Array,
diff --git a/polygerrit-ui/app/elements/change/gr-message/gr-message.js b/polygerrit-ui/app/elements/change/gr-message/gr-message.js
index d2dff927ba..26e0cd380f 100644
--- a/polygerrit-ui/app/elements/change/gr-message/gr-message.js
+++ b/polygerrit-ui/app/elements/change/gr-message/gr-message.js
@@ -22,7 +22,6 @@
 
   Polymer({
     is: 'gr-message',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when this message's reply link is tapped.
diff --git a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.js b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.js
index 50988efdb9..6639b5a0fe 100644
--- a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.js
+++ b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.js
@@ -27,7 +27,6 @@
 
   Polymer({
     is: 'gr-messages-list',
-    _legacyUndefinedCheck: true,
 
     properties: {
       changeNum: Number,
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
index 97241aea2a..76c5980a7e 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-related-changes-list',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a new section is loaded so that the change view can determine
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
index 11141605fd..a78e68f9f4 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
@@ -54,7 +54,6 @@
 
   Polymer({
     is: 'gr-reply-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when a reply is successfully sent.
diff --git a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
index 42bcd0904f..86e76b4d4f 100644
--- a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
+++ b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
@@ -19,7 +19,6 @@
 
   Polymer({
     is: 'gr-reviewer-list',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the "Add reviewer..." button is tapped.
diff --git a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.js b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.js
index 407ef0f376..0cbec84c5c 100644
--- a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.js
+++ b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.js
@@ -25,7 +25,6 @@
 
   Polymer({
     is: 'gr-thread-list',
-    _legacyUndefinedCheck: true,
 
     properties: {
       /** @type {?} */
diff --git a/polygerrit-ui/app/elements/change/gr-upload-help-dialog/gr-upload-help-dialog.js b/polygerrit-ui/app/elements/change/gr-upload-help-dialog/gr-upload-help-dialog.js
index 59eb805e70..092204ad60 100644
--- a/polygerrit-ui/app/elements/change/gr-upload-help-dialog/gr-upload-help-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-upload-help-dialog/gr-upload-help-dialog.js
@@ -29,7 +29,6 @@
 
   Polymer({
     is: 'gr-upload-help-dialog',
-    _legacyUndefinedCheck: true,
 
     /**
      * Fired when the user presses the close button.