- Electron version: 1.3.6
- Operating system: Windows 7 x64
- Other: Microsoft Office 2013 (will make more sense in a bit)

`shell.openItem()` is a blocking call, it would be nice if it's async or has an async version to handle synchronous external application behavior.

Reproduce: 
Open a password-protected Microsoft Excel file, `shell.openItem()` will be blocking until the Password window is submitted or dismissed. Consequently Microsoft Word does not have this issue.

Related to #2761.

shell/browser/ui/inspectable_web_contents_impl.cc
const std::string& message) {}
void InspectableWebContentsImpl::SetEyeDropperActive(bool active) {}
void InspectableWebContentsImpl::ShowCertificateViewer(
    const std::string& cert_chain) {}
void InspectableWebContentsImpl::ZoomIn() {
  double new_level = GetNextZoomLevel(GetDevToolsZoomLevel(), false);
  SetZoomLevelForWebContents(GetDevToolsWebContents(), new_level);
  UpdateDevToolsZoomLevel(new_level);
}
void InspectableWebContentsImpl::ZoomOut() {
  double new_level = GetNextZoomLevel(GetDevToolsZoomLevel(), true);
  SetZoomLevelForWebContents(GetDevToolsWebContents(), new_level);
  UpdateDevToolsZoomLevel(new_level);
}
void InspectableWebContentsImpl::ResetZoom() {
  SetZoomLevelForWebContents(GetDevToolsWebContents(), 0.);
  UpdateDevToolsZoomLevel(0.);
}
void InspectableWebContentsImpl::SetDevicesDiscoveryConfig(
    bool discover_usb_devices,
    bool port_forwarding_enabled,
    const std::string& port_forwarding_config,
    bool network_discovery_enabled,
    const std::string& network_discovery_config) {}
void InspectableWebContentsImpl::SetDevicesUpdatesEnabled(bool enabled) {}