This tab receives ImeRenderWidgetHost pipe #1. The patched renderer stashes
the remote in a process-global. In 4 s this tab navigates cross-origin
to victim.com, which is site-isolated and gets a new renderer
process. Pipe #1's Java receiver is never closed.
Before navigating, open keepalive.html in a second tab so
this renderer process survives the cross-process navigation.