* Electron version: 2.0.0-beta.7
* Operating system: Windows 7

### Expected behavior

`new BrowserWindow({webPreferences:{webSecurity:false}})` should not show mixed-content errors. It should show warnings and continue to load the content.

### Actual behavior

mixed-content errors are shown unless *allowRunningInsecureContent* is specified which is contrary to the documentation:

> Disabling webSecurity will disable the same-origin policy and set allowRunningInsecureContent property to true. 

This was working as expected in 1.8.2

### How to reproduce

Open a new BrowserWindow as above and load a page via `https` that contains elements using `http`.
atom/browser/web_contents_preferences.cc
if (fonts->GetString("monospace", &font))
      prefs->fixed_font_family_map[content::kCommonScript] = font;
    if (fonts->GetString("cursive", &font))
      prefs->cursive_font_family_map[content::kCommonScript] = font;
    if (fonts->GetString("fantasy", &font))
      prefs->fantasy_font_family_map[content::kCommonScript] = font;
  }
  int size;
  if (GetInteger("defaultFontSize", &size))
    prefs->default_font_size = size;
  if (GetInteger("defaultMonospaceFontSize", &size))
    prefs->default_fixed_font_size = size;
  if (GetInteger("minimumFontSize", &size))
    prefs->minimum_font_size = size;
  std::string encoding;
  if (dict_.GetString("defaultEncoding", &encoding))
    prefs->default_encoding = encoding;
}
bool WebContentsPreferences::GetInteger(const base::StringPiece& attribute_name,
                                        int* val) {
  
  if (dict_.GetInteger(attribute_name, val))
    return true;
  std::string str;
  if (dict_.GetString(attribute_name, &str))
    return base::StringToInt(str, val);
  return false;
}
}