* 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
const extensions::SizeConstraints& window_constraints) {
  extensions::SizeConstraints content_constraints(GetContentSizeConstraints());
  if (window_constraints.HasMaximumSize()) {
    gfx::Rect max_bounds = WindowBoundsToContentBounds(
        gfx::Rect(window_constraints.GetMaximumSize()));
    content_constraints.set_maximum_size(max_bounds.size());
  }
  if (window_constraints.HasMinimumSize()) {
    gfx::Rect min_bounds = WindowBoundsToContentBounds(
        gfx::Rect(window_constraints.GetMinimumSize()));
    content_constraints.set_minimum_size(min_bounds.size());
  }
  SetContentSizeConstraints(content_constraints);
}
extensions::SizeConstraints NativeWindow::GetSizeConstraints() {
  extensions::SizeConstraints content_constraints = GetContentSizeConstraints();
  extensions::SizeConstraints window_constraints;
  if (content_constraints.HasMaximumSize()) {
    gfx::Rect max_bounds = ContentBoundsToWindowBounds(
        gfx::Rect(content_constraints.GetMaximumSize()));
    window_constraints.set_maximum_size(max_bounds.size());
  }
  if (content_constraints.HasMinimumSize()) {
    gfx::Rect min_bounds = ContentBoundsToWindowBounds(
        gfx::Rect(content_constraints.GetMinimumSize()));
    window_constraints.set_minimum_size(min_bounds.size());
  }
  return window_constraints;
}
void NativeWindow::SetContentSizeConstraints(