* 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
SetBounds(gfx::Rect(GetPosition(), size), animate);
}
gfx::Size NativeWindow::GetSize() {
  return GetBounds().size();
}
void NativeWindow::SetPosition(const gfx::Point& position, bool animate) {
  SetBounds(gfx::Rect(position, GetSize()), animate);
}
gfx::Point NativeWindow::GetPosition() {
  return GetBounds().origin();
}
void NativeWindow::SetContentSize(const gfx::Size& size, bool animate) {
  SetSize(ContentBoundsToWindowBounds(gfx::Rect(size)).size(), animate);
}
gfx::Size NativeWindow::GetContentSize() {
  return GetContentBounds().size();
}
void NativeWindow::SetContentBounds(const gfx::Rect& bounds, bool animate) {
  SetBounds(ContentBoundsToWindowBounds(bounds), animate);
}
gfx::Rect NativeWindow::GetContentBounds() {
  return WindowBoundsToContentBounds(GetBounds());
}
void NativeWindow::SetSizeConstraints(