Fix A11y read changes description in dashboard

Regressed in Change 329580. For A11y to read row about change, other
rows (gr-change-list-items) need to have tabIndex=-1

Release-Notes: skip
Google-Bug-Id: b/234832728
Change-Id: I45d61f4acf85849b732a0c351a40355d5d85dd11
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-section/gr-change-list-section.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-section/gr-change-list-section.ts
index a7360e3..5e66fff 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-section/gr-change-list-section.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-section/gr-change-list-section.ts
@@ -20,7 +20,6 @@
 import {sharedStyles} from '../../../styles/shared-styles';
 import {Metadata} from '../../../utils/change-metadata-util';
 import {WAITING} from '../../../constants/constants';
-import {ifDefined} from 'lit/directives/if-defined';
 import {provide} from '../../../models/dependency';
 import {
   bulkActionsModelToken,
@@ -296,7 +295,7 @@
   ) {
     const ariaLabel = this.computeAriaLabel(change);
     const selected = this.computeItemSelected(index);
-    const tabindex = this.computeTabIndex(index);
+    const tabIndex = this.computeTabIndex(index);
     return html`
       <gr-change-list-item
         .account=${this.account}
@@ -307,9 +306,10 @@
         .visibleChangeTableColumns=${columns}
         .showNumber=${this.showNumber}
         ?showStar=${this.showStar}
-        tabindex=${ifDefined(tabindex)}
+        tabindex=${tabIndex}
         .labelNames=${this.labelNames}
         aria-label=${ariaLabel}
+        role="button"
       ></gr-change-list-item>
     `;
   }
@@ -346,7 +346,7 @@
 
   private computeTabIndex(index: number) {
     if (this.isCursorMoving) return 0;
-    return this.computeItemSelected(index) ? 0 : undefined;
+    return this.computeItemSelected(index) ? 0 : -1;
   }
 
   // private but used in test