Close new child window if its only navigation was opening a Native app.

There is no reason to keep a bank Tab in case if newly opened window
launched an external app. This behavior is similar to launching native
apps.

BUG=496419

Review URL: https://codereview.chromium.org/1146133005

Cr-Commit-Position: refs/heads/master@{#333120}

ios/web/web_state/ui/crw_web_controller.mm

@@ -2741,7 +2741,8 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
       // Record the URL so that errors reported following the 'NO' reply can be
       // safely ignored.
       [_openedApplicationURL addObject:request.URL];
-      return NO;
+      if ([self cancellable])
+        [_delegate webPageOrderedClose];
     }
     return NO;
   }