- Electron version: v1.3.3
- Operating system: OS X 10.11.6

v1.3.3 broke the detection of the `scroll-touch-begin` and `scroll-touch-end` events for me within a `webview`. It looks like the pull request #6754 caused this issue. v1.3.2 works as expected.

Behavior that I'm observing on v1.3.3:
- Most of the time, the `scroll-touch-*` events are not emitted when the cursor is on top of a `webview`.
- The `scroll-touch-*` events seem to be emitted _only once_ when the cursor is on a `webview` and on a scrollable element. The scrollable elements in my app have no native scrollbar set (they have the style `overflow: hidden;` set instead of `overflow: scroll;`). This is the case in which I need to receive the `scroll-touch-*` events.
- The `scroll-touch-*` events seem to work fine when the cursor is outside of the `webview` tag.

atom/browser/native_window.cc
UINT message, WPARAM w_param, LPARAM l_param) {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_,
                    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() {