- 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/api/atom_api_window.cc
return ContainsKey(messages_callback_map_, message);
}
void Window::UnhookAllWindowMessages() {
  messages_callback_map_.clear();
}
bool Window::SetThumbnailClip(const gfx::Rect& region) {
  auto window = static_cast<NativeWindowViews*>(window_.get());
  return window->taskbar_host().SetThumbnailClip(
      window_->GetAcceleratedWidget(), region);
}
bool Window::SetThumbnailToolTip(const std::string& tooltip) {
  auto window = static_cast<NativeWindowViews*>(window_.get());
  return window->taskbar_host().SetThumbnailToolTip(
      window_->GetAcceleratedWidget(), tooltip);
}
#endif
#if defined(TOOLKIT_VIEWS)
void Window::SetIcon(mate::Handle<NativeImage> icon) {
#if defined(OS_WIN)
  static_cast<NativeWindowViews*>(window_.get())->SetIcon(
      icon->GetHICON(GetSystemMetrics(SM_CXSMICON)),
      icon->GetHICON(GetSystemMetrics(SM_CXICON)));
#elif defined(USE_X11)
  static_cast<NativeWindowViews*>(window_.get())->SetIcon(
      icon->image().AsImageSkia());
#endif
}
#endif
void Window::SetAspectRatio(double aspect_ratio, mate::Arguments* args) {