Inline gr-list-view-mixin stuff and remove it

Google-Bug-Id: b/199305427
Change-Id: I136a6fdce44e175a88bc023b3424bb90fde48088
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index 8f94b38..645e770 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -306,3 +306,5 @@
 }
 
 export const RELOAD_DASHBOARD_INTERVAL_MS = 10 * 1000;
+
+export const SHOWN_ITEMS_COUNT = 25;