* 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& size_constraints) {
  size_constraints_ = size_constraints;
}
extensions::SizeConstraints NativeWindow::GetContentSizeConstraints() {
  return size_constraints_;
}
void NativeWindow::SetMinimumSize(const gfx::Size& size) {
  extensions::SizeConstraints size_constraints;
  size_constraints.set_minimum_size(size);
  SetSizeConstraints(size_constraints);
}
gfx::Size NativeWindow::GetMinimumSize() {
  return GetSizeConstraints().GetMinimumSize();
}
void NativeWindow::SetMaximumSize(const gfx::Size& size) {
  extensions::SizeConstraints size_constraints;
  size_constraints.set_maximum_size(size);
  SetSizeConstraints(size_constraints);
}
gfx::Size NativeWindow::GetMaximumSize() {
  return GetSizeConstraints().GetMaximumSize();
}
void NativeWindow::SetSheetOffset(const double offsetX, const double offsetY) {
  sheet_offset_x_ = offsetX;
  sheet_offset_y_ = offsetY;
}
double NativeWindow::GetSheetOffsetX() {