Don't stop loading for overscroll refresh action.

StopLoading() discards non-committed items, meaning that a refresh
for a pending load would reload the previous page rather than retrying
the pending load.

Bug: 787795
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I186fdd847d7a738dec6cb62125ff83c491a3ae72
Reviewed-on: https://chromium-review.googlesource.com/794014Reviewed-by: Eugene But <eugenebut@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519778}

ios/chrome/browser/ui/browser_view_controller.mm

@@ -3395,19 +3395,9 @@ bubblePresenterForFeature:(const base::Feature&)feature
     case OverscrollAction::CLOSE_TAB:
       [self.dispatcher closeCurrentTab];
       break;
-    case OverscrollAction::REFRESH: {
-      web::WebState* webState = [_model currentTab].webState;
-      if (webState) {
-        if (webState->IsLoading()) {
-          webState->Stop();
-        }
-        // |check_for_repost| is true because the reload is explicitly initiated
-        // by the user.
-        webState->GetNavigationManager()->Reload(web::ReloadType::NORMAL,
-                                                 true /* check_for_repost */);
-      }
+    case OverscrollAction::REFRESH:
+      [self reload];
       break;
-    }
     case OverscrollAction::NONE:
       NOTREACHED();
       break;