- 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
brightray::InspectableWebContents* inspectable_web_contents,
    const mate::Dictionary& options,
    NativeWindow* parent)
    : content::WebContentsObserver(inspectable_web_contents->GetWebContents()),
      has_frame_(true),
      transparent_(false),
      enable_larger_than_screen_(false),
      is_closed_(false),
      sheet_offset_x_(0.0),
      sheet_offset_y_(0.0),
      aspect_ratio_(0.0),
      parent_(parent),
      is_modal_(false),
      inspectable_web_contents_(inspectable_web_contents),
      weak_factory_(this) {
  options.Get(options::kFrame, &has_frame_);
  options.Get(options::kTransparent, &transparent_);
  options.Get(options::kEnableLargerThanScreen, &enable_larger_than_screen_);
  if (parent)
    options.Get("modal", &is_modal_);
#if defined(OS_LINUX) || defined(OS_WIN)
  auto* prefs = web_contents()->GetMutableRendererPrefs();