[SiteEngagement WebUI] Replace C++ browser test with JS version.

chrome/browser/resources/engagement/site_engagement.js

Index: chrome/browser/resources/engagement/site_engagement.js
diff --git a/chrome/browser/resources/engagement/site_engagement.js b/chrome/browser/resources/engagement/site_engagement.js
index 2578317f217b1f2ff350c573e1abf804523efc91..cb40bf4d1445bfaa0c27d98b19bc2a157c0454a9 100644
--- a/chrome/browser/resources/engagement/site_engagement.js
+++ b/chrome/browser/resources/engagement/site_engagement.js
@@ -120,7 +120,7 @@ define('main', [
      */
     function handleBaseScoreChange(origin, e) {
       var baseScoreInput = e.target;
-      uiHandler.setSiteEngagementScoreForUrl(origin, baseScoreInput.value);
+      uiHandler.setSiteEngagementBaseScoreForUrl(origin, baseScoreInput.value);
       baseScoreInput.barCellRef.style.width = (baseScoreInput.value * 4) + 'px';
       baseScoreInput.blur();
       enableAutoupdate();
@@ -195,8 +195,6 @@ define('main', [
 
         engagementTableBody.appendChild(createRow(info));
       });
-
-      resolvePageIsPopulated();
     }
 
     /**
@@ -207,6 +205,7 @@ define('main', [
       uiHandler.getSiteEngagementDetails().then((response) => {
         info = response.info;
         renderTable(info);
+        resolvePageIsPopulated();
       });
     };