It doesn't look very good for "native" apps to overscroll when scrolling. Would be nice to have a BrowserWindow option to disable overscroll

![untitled12](https://cloud.githubusercontent.com/assets/170270/15033357/fc36e32e-1293-11e6-8cdc-6c17b0f504dd.gif)
## 
- Electron version: 0.37.8
- Operating system: OS X 10.11.4

atom/browser/web_contents_preferences.cc
}
  if (self->web_preferences_.GetBoolean("allowDisplayingInsecureContent", &b))
    prefs->allow_displaying_insecure_content = b;
  if (self->web_preferences_.GetBoolean("allowRunningInsecureContent", &b))
    prefs->allow_running_insecure_content = b;
  const base::DictionaryValue* fonts = nullptr;
  if (self->web_preferences_.GetDictionary("defaultFontFamily", &fonts)) {
    base::string16 font;
    if (fonts->GetString("standard", &font))
      prefs->standard_font_family_map[content::kCommonScript] = font;
    if (fonts->GetString("serif", &font))
      prefs->serif_font_family_map[content::kCommonScript] = font;
    if (fonts->GetString("sansSerif", &font))
      prefs->sans_serif_font_family_map[content::kCommonScript] = font;
    if (fonts->GetString("monospace", &font))
      prefs->fixed_font_family_map[content::kCommonScript] = font;
  }
  int size;
  if (self->web_preferences_.GetInteger("defaultFontSize", &size))
    prefs->default_font_size = size;
  if (self->web_preferences_.GetInteger("defaultMonospaceFontSize", &size))
    prefs->default_fixed_font_size = size;
  if (self->web_preferences_.GetInteger("minimumFontSize", &size))
    prefs->minimum_font_size = size;
  std::string encoding;
  if (self->web_preferences_.GetString("defaultEncoding", &encoding))
    prefs->default_encoding = encoding;
}
}