[ios] Remove early return in FullscreenControllerImpl::SetWebStateList

This is needed for Fullscreen to reset itself when a navigation occurs.

Bug: 790886
Change-Id: I8ac3cb22679e5f2dfc5f966797513d67e8b08da0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2132627Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755503}

ios/chrome/browser/ui/fullscreen/fullscreen_controller_impl.mm

@@ -176,10 +176,6 @@ ChromeBroadcaster* FullscreenControllerImpl::broadcaster() {
 }
 
 void FullscreenControllerImpl::SetWebStateList(WebStateList* web_state_list) {
-  if (fullscreen::features::ShouldScopeFullscreenControllerToBrowser())
-    // If FullscreenController is Browser-scoped, then WebStateList observation
-    // should last the entire lifetime of the Browser.
-    return;
   web_state_list_observer_.SetWebStateList(web_state_list);
 }