Add missing "Show trailing whitespace" to edit preference

Change-Id: I06c5e8a55aed877bcdef7f4a72a8771ad77f734c
diff --git a/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.ts b/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.ts
index 4909bef..7cfd1b3 100644
--- a/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.ts
+++ b/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.ts
@@ -35,6 +35,7 @@
     showMatchBrackets: HTMLInputElement;
     editShowLineWrapping: HTMLInputElement;
     editShowTabs: HTMLInputElement;
+    editShowTrailingWhitespaceInput: HTMLInputElement;
   };
 }
 @customElement('gr-edit-preferences')
@@ -89,6 +90,14 @@
     this._handleEditPrefsChanged();
   }
 
+  _handleEditShowTrailingWhitespaceTap() {
+    this.set(
+      'editPrefs.show_whitespace_errors',
+      this.$.editShowTrailingWhitespaceInput.checked
+    );
+    this._handleEditPrefsChanged();
+  }
+
   _handleMatchBracketsChanged() {
     this.set('editPrefs.match_brackets', this.$.showMatchBrackets.checked);
     this._handleEditPrefsChanged();
diff --git a/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences_html.ts b/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences_html.ts
index a51deaf..abd925f 100644
--- a/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences_html.ts
+++ b/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences_html.ts
@@ -85,6 +85,19 @@
       </span>
     </section>
     <section>
+      <label for="showTrailingWhitespaceInput" class="title"
+        >Show trailing whitespace</label
+      >
+      <span class="value">
+        <input
+          id="editShowTrailingWhitespaceInput"
+          type="checkbox"
+          checked$="[[editPrefs.show_whitespace_errors]]"
+          on-change="_handleEditShowTrailingWhitespaceTap"
+        />
+      </span>
+    </section>
+    <section>
       <label for="showMatchBrackets" class="title">Match brackets</label>
       <span class="value">
         <input