[iOS] Reset FullscreenModel when tapping status bar

The button catching the taps when the toolbar is collapsed doesn't catch
the taps on the status bar.
This CL makes sure the toolbar is expanded when the status bar is
tapped.

Bug: 878382
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs
Change-Id: I71dd7af9ca7d2e47687887d69f11661c71e3d86c
Reviewed-on: https://chromium-review.googlesource.com/1199162Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590259}

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

@@ -63,6 +63,7 @@
     self.mediator->ScrollToTop();
     return YES;
   } else {
+    self.mediator->AnimateModelReset();
     return NO;
   }
 }