[ios] Fix bug with badges not showing up

The badge tab helper's delegate needs to be set on
initialization, otherwise it the mediator won't be informed
of badge updates until after the active WebState is reset.

Change-Id: Ie2774f2d0dc1929e9489c12a7e8cac6cca007794
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2026729Reviewed-by: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Auto-Submit: David Jean <djean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736556}

ios/chrome/browser/ui/badges/badge_mediator.mm

@@ -86,6 +86,9 @@ const int kMinimumNonFullScreenBadgesForOverflow = 2;
     // Set up the WebStateList and its observer.
     _webStateList = browser->GetWebStateList();
     _webState = _webStateList->GetActiveWebState();
+    if (_webState) {
+      InfobarBadgeTabHelper::FromWebState(_webState)->SetDelegate(self);
+    }
     _webStateListObserver = std::make_unique<WebStateListObserverBridge>(self);
     _webStateList->AddObserver(_webStateListObserver.get());
   }