cr run headless_shell -window-size=800x600 --no-sandbox --deterministic-fetch --screenshot  http://example.com
Contains a screenshot containing the stylesheet.

I notice a possible mojo problem:

[1114/141929:ERROR:interface_registry.cc(210)] Failed to locate a binder for interface: media::mojom::RemoterFactory requested by: service:content_renderer exposed by: service:content_browser via InterfaceProviderSpec "navigation:frame".

InterfaceRegistry(navigation:frame):
Owned by:
  service:content_browser@ run as: 66a28f83-53b3-4193-b8ed-cefab19c4a67

  Providing:
    capability: renderer containing interfaces:
      autofill::mojom::AutofillDriver
      autofill::mojom::PasswordManagerDriver
      blink::mojom::MediaSessionService
      blink::mojom::PermissionService
      blink::mojom::PresentationService
      blink::mojom::SensitiveInputVisibilityService
      blink::mojom::ShapeDetection
      blink::mojom::WebBluetoothService
      blink::mojom::WebSocket
      content::mojom::BrowserTarget
      device::VibrationManager
      device::mojom::GeolocationService
      device::mojom::SensorProvider
      device::mojom::VRService
      device::mojom::WakeLockService
      device::nfc::mojom::NFC
      device::usb::DeviceManager
      embedder_test::TestEmbedderService
      media::mojom::InterfaceFactory
      media::mojom::RemoterFactory
      media::mojom::Renderer
      mojom::MediaDevicesDispatcherHost
      payments::mojom::PaymentRequest

  Requiring:
    From: service:content_renderer:
      browser

Bound to:
  service:content_renderer@3_1 run as: 66a28f83-53b3-4193-b8ed-cefab19c4a67

  Providing:
    capability: browser containing interfaces:
      blink::mojom::AppBannerController
      content::mojom::ImageDownloader
      mojom::MediaDevicesListener

  Requiring:
    From: service:content_browser:
      renderer

Binders registered for:
 * blink::mojom::MediaSessionService
 * blink::mojom::PermissionService
 * blink::mojom::PresentationService
 * blink::mojom::WebBluetoothService
 * blink::mojom::WebSocket
 * device::VibrationManager
 * device::mojom::GeolocationService
 * device::mojom::WakeLockService
 * media::mojom::InterfaceFactory
 * mojom::MediaDevicesDispatcherHost

 * - denotes an interface exposed to remote per policy.