* Electron version: 1.6.0
* Operating system: MacOS 10.12.2

### Expected behavior

'scroll-touch-end' emits when trackpad scrolling ends.

### Actual behavior

The begin event emits, but not the end

### How to reproduce

Example repo: https://github.com/pfrazee/electron-bug-no-scroll-touch-end

atom/browser/native_window.cc
UINT message, WPARAM w_param, LPARAM l_param) {
  for (NativeWindowObserver& observer : observers_)
    observer.OnWindowMessage(message, w_param, l_param);
}
#endif
std::unique_ptr<SkRegion> NativeWindow::DraggableRegionsToSkRegion(
    const std::vector<DraggableRegion>& regions) {
  std::unique_ptr<SkRegion> sk_region(new SkRegion);
  for (const DraggableRegion& region : regions) {
    sk_region->op(
        region.bounds.x(),
        region.bounds.y(),
        region.bounds.right(),
        region.bounds.bottom(),
        region.draggable ? SkRegion::kUnion_Op : SkRegion::kDifference_Op);
  }
  return sk_region;
}
void NativeWindow::RenderViewCreated(
    content::RenderViewHost* render_view_host) {
  if (!transparent_)
    return;
  content::RenderWidgetHostImpl* impl = content::RenderWidgetHostImpl::FromID(
      render_view_host->GetProcess()->GetID(),
      render_view_host->GetRoutingID());
  if (impl)
    impl->SetBackgroundOpaque(false);
}
void NativeWindow::BeforeUnloadDialogCancelled() {