Show info when adding reviewers to private change

Show info that the private change will be visible to the user
added as reviewer/CC when they are added in the reply dialog.

Google-bug-id: b/259515557
Release-Notes: skip
Screenshot: https://imgur.com/a/qAi0yrW
Change-Id: I9c5e11194db57a4d7e080c33f14297611bbf1e55
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
index 29bd1d9..11406b4 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
@@ -111,7 +111,7 @@
   LabelNameToValuesMap,
   PatchSetNumber,
 } from '../../../api/rest-api';
-import {css, html, PropertyValues, LitElement} from 'lit';
+import {css, html, PropertyValues, LitElement, nothing} from 'lit';
 import {sharedStyles} from '../../../styles/shared-styles';
 import {when} from 'lit/directives/when.js';
 import {classMap} from 'lit/directives/class-map.js';
@@ -606,6 +606,16 @@
       .patchsetLevelContainer.unresolved {
         background-color: var(--unresolved-comment-background-color);
       }
+      .privateVisiblityInfo {
+        display: flex;
+        justify-content: center;
+        background-color: var(--info-background);
+        padding: var(--spacing-s) 0;
+      }
+      .privateVisiblityInfo gr-icon {
+        margin-right: var(--spacing-m);
+        color: var(--info-foreground);
+      }
     `,
   ];
 
@@ -791,6 +801,7 @@
             <gr-endpoint-slot name="below"></gr-endpoint-slot>
           </gr-endpoint-decorator>
           ${this.renderCCList()} ${this.renderReviewConfirmation()}
+          ${this.renderPrivateVisiblityInfo()}
         </section>
         <section class="labelsContainer">${this.renderLabels()}</section>
         <section class="newReplyDialog textareaContainer">
@@ -893,6 +904,22 @@
     `;
   }
 
+  private renderPrivateVisiblityInfo() {
+    const addedAccounts = [
+      ...(this.reviewersList?.additions() ?? []),
+      ...(this.ccsList?.additions() ?? []),
+    ];
+    if (!this.change?.is_private || !addedAccounts.length) return nothing;
+    return html`
+      <div class="privateVisiblityInfo">
+        <gr-icon icon="info"></gr-icon>
+        <div>
+          Adding a reviewer/CC will make this private change visible to them
+        </div>
+      </div>
+    `;
+  }
+
   private renderLabels() {
     if (!this.change || !this.account || !this.permittedLabels) return;
     return html`